Started Steins;Gate

You'll get this achievement as soon as you boot up the game and get to the main menu

Prologue Clear

Story-related and cannot be missed!
The prologue is fairly short and there are no choices to be made, so it's mostly just a question about reading through it.

Chapter 1 Clear
Story-related and cannot be missed!
The first chapter is kind of convoluted in explanations and setting up plot, but there aren't a lot of choices, at least not a lot of choices that really matters. This is also the chapter you get: "Homerun-level Clumsiness", "RaiNet's Mascot", half of "Princesses of Chaos", and a fifth of "Hero of RaiNet".

Chapter 2 Clear
Story-related and cannot be missed!
Not a lot to talk about chapter 2. There are a few decisions to take note of, and the chapter itself is one of the slower ones (except for one pretty bone-chilling moment). This is also where you get "Cruel Sister", a third of "Songs of Chaos", and a few choice-specific CG's.

Chapter 3 Clear
Story-related and cannot be missed!
Chapter 3 is where things start to get up to speed. Here you will also be able to get one third of "Songs of Chaos", one fifth of "Hero of RaiNet" and one third of "Froggy Fad Demise".

Chapter 4 Clear
Story-related and cannot be missed!
Chapter 4 has by far the most choice-specific events in the game. Not only does the first True Ending checkpoint appear in this chapter, but you also need to get "Genius Girl's Melancholy", "Discontinuous Qualia", "Cat's Tea Time", and the last three thirds of "Hero of RaiNet".

Chapter 5 Clear
Story-related and cannot be missed!
Chapter 5 is kind of annoying achievement-wise, since some of the choice-specific events requires you to get the True Ending checkpoint, and some require you to not get them. In this chapter there is another True Ending checkpoint, as well as, "Passions Best Forgotten", the second half of "Princesses of Chaos", and the last third of "Songs of Chaos".

Chapter 6 Clear
Story-related and cannot be missed as long as you don't get an ending before this chapter is done!
Chapter 6 has the first ending, Suzuha's to be specific. Chapter 6 is probably also the longest chapter. Despite that there is only one choice for a CG, and then the choice for the ending.

Chapter 7 Clear
Story-related and cannot be missed as long as you don't get an ending before this chapter is done!
Chapter 7 is a bit more return to form. It has the most complex e-mail, dialogue tree so watch out for that one. In this chapter there is another True Ending checkpoint, as well as, the last two thirds of "Froggy Fad Demise", and Faris' Ending.
Chapter 8 Clear
Story-related and cannot be missed as long as you don't get an ending before this chapter is done!
This is a pretty sweet, and relatively short chapter. It only has a choice for a True Ending checkpoint, and Luka's Ending.

Chapter 9 Clear
Story-related and cannot be missed as long as you don't get an ending before this chapter is done!
Chapter 9 is probably the least choice-specific chapter. There is a choice for a CG, and a True Ending checkpoint. That's it. The chapter itself is pretty intense though. We are nearing the end so that's natural. Also remember that the ending after chapter 10 is based on how many of the True Ending checkpoints you've gotten, and there is another one in chapter 10 as well.

[Phone Trigger] Viewed email send history at least once
Pretty much unmissable. You pull out your phone by pressing relevant button and then you can do that almost any time you want. Just press the upper left button on the phone and there you go.

[Phone Trigger] Read an email
Pretty much unmissable. You pull out your phone by pressing relevant button and then you can do that almost any time you want. Just press the upper left button on the phone and then choose an e-mail to read and pick that, and you will get this.

[Phone Trigger] Replied to an email
You pull out your phone by pressing relevant button and then you can do that almost any time you want. Not all e-mails can be replied to. Some e-mails have highlighted blue text .Those words or sentences can be selected and you will send a reply concerning that specific block of text. This is also how you get most of the misc. trophies in this game. Just send a reply to an e-mail and you will get this achievement.

[Phone Trigger] Cleared someone's mail without reading it
This one is a bit trickier. There are no manual way to clear an e-mail, but there are points in the story where e-mails get cleared (like endings, but there are also some in the middle of the story as well). If you pass one of those points in the story while having an e-mail that is unread you will get this achievement.

[Phone Trigger] Changed phone wallpaper
You pull out your phone by pressing relevant button and then you can do that almost any time you want. Press the lower right button. Choose "Change Wallpaper", press a wallpaper and then press "Set as Ringtone" (why ringtone I don't know. Probably an oversight on the developers part), and there you go.

[Phone Trigger] Changed ringtone
You pull out your phone by pressing relevant button and then you can do that almost any time you want. Press the lower right button. Choose either "Ringtone for Call" or "Ringtone for Mail", and then choose a ringtone and then press "Set as ringtone" and you will get the achievement.

[Phone Trigger] Ignored a phone call
Throughout the story you will several phone calls. Some can be ignored, some can't. Some contains CG's and misc. trophies, some don't. The first phone call you are able to ignore is in chapter 2, when Mayuri calls you while you're in the shopping district, however, that one has both CG's and a misc. trophy tied to it, so you may want to either save before ignoring it or just wait until the end of chapter 3 where Daru calls you and choosing to either ignore or answer it has no impact on anything related to the platinum achievement or the story.

[Phone Trigger] Asked by Kurisu to buy cup noodles twice in a row
Choice-specific!

Chapter 4

Type: E-mail
Sender: Kurisu

- You will get an e-mail titled: "Did you write it?"

• Reply to "Report".

- A good while later you will get a reply titled: "Please?"

• Reply to "Cup noodles".

- You will then get a reply titled: "Favor to ask"

• Read it (you don't have to reply (but replying won't hurt).

[Phone Trigger] Learned why Mayuri started making costumes
Choice-specific!
You can only get this achievement if you ignore the first True Ending checkpoint in chapter 4. If you that, then Mayuri will send you an e-mail in chapter 5 titled: "What made me happy today"

Chapter 5

Type: E-mail
Sender: Mayuri
Prerequisite: Have Not passed any True Ending Checkpoints

- If the prerequisites are met you will get an e-mail from Mayuri titled: "What made me happy today."

• Reply to: "Cosplay"

- A little later you will get a reply titled: "The reason".

• Read it.

[Phone Trigger] Received an unusual proposition from Suzuha
Choice-specific!

Chapter 4

Type: E-mail
Sender: Suzuha

- You will get an e-mail from Suzuha titled: "Akihabara's".

• Reply to "Peaceful"

- You will a little while later get a reply titled: "Now, on TV".

• Read it.

Learned about Luka's relationship to his sister
Choice-specific!

Chapter 2

Type: E-mail & Call
Sender: Luka

- You will receive an e-mail titled: "I made sweets."

• Reply to "Family".

- While in the shopping streets of Akiba a little later on, you will get a call from Mayuri.

• Answer it.

- You will get a reply to your e-mail titled: "My family".

• Reply to "My sister".

- You will then get a reply titled: "About my sister".

• Read it.

[Phone Trigger] Offered tea by Faris
Choice-specific!

Chapter 4

Type: E-mail
Sender: Faris

- You will get an e-mail from Faris titled: "Sign of increasing misfortune"

• Reply to "He".

- You will later get a reply titled: "About abilities"

• Reply to "NyanNyanian"

- A while later you will get a reply titled: "Cat tongue nya"

• Read it.

Made friends with Kurisu via email
Choice-specific!

This is gotten in chapter 4, and is the first objective to get the True Ending.

Chapter 4

Type: E-mail
Sender: Kurisu

- You will get an e-mail titled: "Did you write it?"

• Reply to "Scientist".

- You will then get a reply titled: "Scientist???"

• Reply to "Bad scientist"

- You will then get a reply titled: "Bad scientist".

• Reply to "Do better".

- You will get a reply a good while later titled: "Home Alone"

• Reply to "Outsider".

- You will then get a reply titled: "Ehhh?"

• Reply to "Disgrace".

- You will then get a reply titled: "Staring at my hand"

• Reply to "Why am I still here?"

- You will then get a reply titled: "Being here"

• Read it.

[Phone Trigger] Received all 13 RaiNet episode summaries
Choice-specific!

Chapter 1

Type: E-mail
Sender: Mayuri

- You will then get a third e-mail later titled: "It's Interesting"

• Open the attachment for "Hero of RaiNet" (1/5).

Chapter 3

"Hero of RaiNet" (2/5)
Type: E-mail
Sender: Faris

- You will get an e-mail titled: "PHANTASM is the cat's meow"

• Reply to "Theme Song".

- You will get a reply titled: "RaiNet OP 2."

• Reply to "RaiNet Kakeru"

- You will then get a reply titled: "RaiNet Ep. 13".

• Open the attachment and go through all of the pages.

Chapter 4

"Hero of RaiNet" (3/5)
Type: E-mail
Sender: Mayuri

- Towards the beginning of the chapter you will get an e-mail titled: "Speaking of lotteries".

• Reply to "Magazines"

- A good while later you will get a reply titled: "Going out? Lelele."

• Reply to "Crunchy-kun"

- A good while later again you will get another reply titled: "About Luka-Chan."

• Reply to "Kakeru-kun"

- A little later you will get another reply titled: "Kakeru-kun"

• Open the attachment and go through all of the pages.

"Hero of RaiNet" (4/5)
Type: E-mail
Sender: Luka

- Not far from the beginning of the chapter you will get an e-mail titled: "About RaiNet".

• Open the attachment and go through all of the pages.

"Hero of RaiNet" (5/5)
Type: E-mail
Sender: Faris

- You will get an e-mail from Faris titled: "Sign of increasing misfortune"

• Reply to "He".

- You will later get a reply titled: "About abilities"

• Reply to "Chinchilla Star"

- A while later you will get a reply titled: "Re: Re: Ep. 8"

• Reply to "Ep. 8"

- A little while later you will get a reply titled: "About ep. 8"

• Open the attachment and go through all of the pages.

[Phone Trigger] Received all Gero Froggy wallpapers
Choice-specific!

Chapter 3

"Froggy Fad Demise" (1/3)
Type: E-mail
Sender: Luka

- You'll receive an e-mail titled: "About Frogs"

• Reply to "Gero Froggies".

- You'll receive a reply titled: "More news about the frogs".

• Open the attachment and go through all of the wallpapers.

Chapter 7

"Froggy Fad Demise" (2/3)
Type: E-mail
Sender: Kurisu
Prerequisite: Pass previous True Ending checkpoints

- If the prerequisites are met you will get an e-mail from Kurisu titled: "The key (ﾉД `)".

• Reply to: "I don't have a key"

- You'll get a reply titled: "( ° д ° )"

• Reply to: "Frog".

- You'll get a reply titled: "Gero Froggy"

• Open the attachment.

"Froggy Fad Demise" (3/3)

- If the prerequisites are met you will get an e-mail from Kurisu titled: "The key (ﾉД `)".

• Reply to: "Home"

- You'll then get a reply titled: "Home"

• Reply to: "Hyahha"

- A long while later you will get another reply titled: "GOGOGOGOGOGO".

• Reply to: "I'm gonna give it to you straight"

- A little while later you will get another reply titled: "Blazing Heart".

• Open the attachment.

[Phone Trigger] Received 3 songs from a chaotic head
Choice-specific!

Chapter 2

"Songs of Chaos" (1/3)
Type: E-mail
Sender: Faris

- You'll receive an e-mail titled: "Original Sin level rising to 180%".

• Reply to "2000".

- Later you will get a reply titled: "Song of Prophecy".

• Open the attachment.

Chapter 3

"Songs of Chaos" (2/3)
Type: E-mail
Sender: Faris

- You will get an e-mail titled: "PHANTASM is the cat's meow"

• Reply to "PHANTASM"

- You will get a reply titled: "The vocalist is a beautiful girl"

• Reply to "Chaos"

- You will get a reply titled: "Re: Re: The vocalist is a beautiful girl"

• Open the attachment, and make sure that a couple of seconds play of each song for the game to register.

Chapter 5

"Songs of Chaos" (3/3)
Type: E-mail
Sender: Faris

- Towards the end of the chapter you will get an e-mail titled: "ComiMa".

• Reply to "Collapsing".

- A little while later you will get a reply titled: "Re: Re: ComiMa"

• Open the attachment.

[Phone Trigger] Received 2 Upa wallpapers
Choice-specific!

Type: E-mail
Sender: Mayuri

- You will get an e-mail titled "Upa..."

• Reply to "Upa"

- Another e-mail will be send titled "Don't Sell It ><" later.

• Open the attachment for "RaiNet's Mascot".

• Reply to "Kakeru-kun".

[Phone Trigger] Received 3 wallpapers of characters from a chaotic head
Choice-specific!

Chapter 1

"Princesses of Chaos" (1/2)

Type: E-mail
Sender: Faris

- Late in the chapter you will get an e-mail titled "The Final Battle is Close at Hand".

• Reply to "Red Southern Cross".

- You'll receive another e-mail titled "So that was it after all, nya".

• Open the attachment.

Chapter 5

"Princesses of Chaos" (2/2)

Type: E-mail
Sender: Mayuri
Prerequisite: Have Not passed any True Ending Checkpoints

- If the prerequisites are met you will get an e-mail from Mayuri titled: "What made me happy today."

• Reply to: "Fubuki-chan and Kaede-chan"

- You will get a reply titled: "Huh?".

• Open the attachment and go through all of the pictures.

Made 10 mistakes while attempting to set the PhoneWave (name subject to change timer)
Choice-specific!
Type: N/A
Sender: N/A

You can get this two places in chapter 1. There will two points in the chapter where you need to type in "120#" on a numpad to start the PhoneWave. Instead of doing that, press the wrong thing ten times.

Unlocked 25% of CGs

get 25% CG Artworks in the "Extras"
Unlocked 50% of CGs

get 50% CG Artworks in the "Extras"
Unlocked 75% of CGs

get 75% CG Artworks in the "Extras"
Unlocked 100% of CGs

CG's are computer graphics. They are the "special art" of the game. Most of the time, it's just a layer with character art put on top of a background, but the CG's are picture of characters actually painted ON the environment. There are 77 of these in total. They can be viewed in the "Extras" menu after getting your first ending. Most of these comes from just completing the stories. They will also require you to get every single ending, and there are even a few CG's that requires you to do some certain choices. The last CG will unlock once you have all of the other CG's. To get it, start a new game, skip past the prologue and as soon as you have access to your phone you can find it by opening an attachment in an e-mail sent to your phone.

Reached Suzuha's ending

Type: E-mail
Receiver: PhoneWave

Towards the end of Chapter 6 you will have to make a choice concerning Suzuha. It's fairly obvious when you get there. You can then either choose to send or not send an e-mail. Send it to progress the novel, don't send it for Suzuha's Ending

Reached Faris's ending

Type: E-mail
Receiver: PhoneWave

Towards the end of Chapter 7 you will have to make a choice concerning Faris. It's fairly obvious when you get there. You can then either choose to send or not send an e-mail. Send it to progress the novel, don't send it for Faris' Ending.

Reached Luka's ending

Type: E-mail
Receiver: PhoneWave

Towards the end of Chapter 8 you will have to make a choice concerning Luka. It's fairly obvious when you get there. You can then either choose to send or not send an e-mail. Send it to progress the novel, don't send it for Luka's Ending.

Reached Mayuri's ending
Type: N/A
Sender: Mayuri
Prerequisite: Do not pass any True Ending checkpoints.

For this ending you need to get to chapter 10 without triggering any other endings, while avoiding all of the True Ending checkpoints. So, when you get to chapter 4 and you get an e-mail from Kurisu titled: "Did you write it?", just simply ignore it. At the end of chapter 10, you will get this ending.

Reached Kurisu's ending
Type: N/A
Sender: Kurisu
Prerequisite: Pass 1-5 True Ending checkpoints.

If you've met the requirements you will get Kurisu's ending at the end of the chapter. If you get an e-mail from Kurisu titled: "Where are you now?", ignore it.

Completed all endings

You just have to get all the endings.
There are a total of 6 endings, including a True End (which is the canonical ending)

• Faris's ending

• Luka's ending

• Suzuha's ending

• Mayuri's ending

• Kurisu's ending

• True Ending

Reached Steins Gate
True Ending!

Chapter 4

Achievements: Genius Girl's Melancholy & Beginning of the True Ending: Checkpoint (1/6)
Type: E-mail
Sender: Kurisu

- You will get an e-mail titled: "Did you write it?"

• Reply to "Scientist".

- You will then get a reply titled: "Scientist???"

• Reply to "Bad scientist"

- You will then get a reply titled: "Bad scientist".

• Reply to "Do better".

- You will get a reply a good while later titled: "Home Alone"

• Reply to "Outsider".

- You will then get a reply titled: "Ehhh?"

• Reply to "Disgrace".

- You will then get a reply titled: "Staring at my hand"

• Reply to "Why am I still here?"

- You will then get a reply titled: "Being here"

• Read it.

Chapter 5

True Ending: Checkpoint (2/6)

Type: E-mail
Sender: Kurisu
Prerequisite: Pass previous True Ending checkpoint

- If prerequisites are met you will get an e-mail from Kurisu titled: "Plans"

• Reply to "Travelling expenses"

- You will a little later get an reply titled: "Idiot!"

• Read it.

- You will a little later get an e-mail titled: "( ´ · ω · `)"

• Read it.

Chapter 7

True Ending: Checkpoint (3/6)

Type: E-mail
Sender: Kurisu
Prerequisite: Pass previous True Ending checkpoints

- If the prerequisites are met you will get an e-mail from Kurisu titled: "The key (ﾉД `)".

• Reply to: "I don't have a key"

- You'll get a reply titled: "( ° д ° )"

• Reply to "Security"

- A good while later you will get a reply titled: "You're delusional, I know".

• Reply to "Reality"

- A little later you will get a reply titled: "Reality"

• Read it.

Chapter 8

True Ending: Checkpoint (4/6)

Type: E-mail
Sender: Kurisu
Prerequisite: Pass all previous True Ending checkpoints

- If the prerequisites are met you will get an e-mail from Kurisu titled: "Explain yourself!"

• Read it. You don't have to reply to it, but it doesn't hurt either.

- Later Kurisu will send another e-mail titled: "From an unpopular girl".

• Read it.

Chapter 9

True Ending: Checkpoint (5/6)

Type: E-mail
Sender: Kurisu
Prerequisite: Pass all previous True Ending checkpoints

- Late in the chapter you will get an e-mail from Kurisu titled: "Contact me, idiot!"

• Reply to "Worried".

- Later you will get a reply titled: "Re: Re: Contact me, idiot!"

• Read it.

Chapter 10

True Ending: Checkpoint (6/6)

Type: N/A
Sender: Kurisu
Prerequisite: Pass all previous True Ending checkpoints

- If the prerequisite is met, you will get an e-mail from Kurisu towards the middle of the chapter titled: "Where are you now?"

• Reply to: "Where you are"

Unlocked all achievements (Platinum)

Once you've reached Steins;Gate and gotten every other achievement in the game you will receive this.