For the Annoy ATG achievement just click on the "A" icon at the corner of the screen a few times until the screen turns a devilish red (I'm calling it Hell mode from now on).
Then, type "SORRY" on your keyboard so it turns back to normal and that will unlock the Apologize to ATG achievement.

For this one you have to zoom out the screen all the way and search on the bottom-left corner (away from the steam machine) for a message that says "Why are you out here?". It's not that hard to find and the achievement should unlock automatically.
Afterwards, you can just right-click with the mouse so that the machine is re-centered in the frame.

So far there's only the Speed Demon and Speed Devil achievements that are related to the max rpm you can reach with the machine.
The process is pretty much the same for both, but as far as I can tell, the Speed Devil one can only be achieved in Hell mode.
First you're going to disable the relief valve by pressing "X", then turn the heat to 100% and fill the water tank with the "L" key (TIP: you can hold L and click on any other application on your desktop so that the tank can be continuously refilled). Wait until the pressure builds up to a max of 350 PSI, then release the brake and open the throttle valve until it sits around 42~43%. I was able to constantly reach around 3518 rpm with this method.
[Note: Since the new update v0.1.20a, it looks like the process to keeping the water tank constantly filled is a bit different. It seems like simply leaving the water valve open should suffice but further testing is needed]
In the meantime, this guide by b94_12vCNZ has been working for me to get 3500 rpm (just DO NOT open the throttle valve more than 60% or you risk losing all the pressure you've built up).

Just leave the game running on the background while the engine works at max speed and max water capacity (just use the tip from the previous section for this one). Eventually you will unlock all of the "boil water" and "x number of revolutions" related achievements.
I was able to unlock the last achievement, Steam Freak in about 31 hours with this method.

Credits to Zehn and his "How to get partial and high vacuum achievements" guide for these two.

First, enter Hell mode and press X on the keyboard to disable the relief valve (DO NOT open the throttle valve). Then, set the heat to 100% and wait until temp maxes at 300ºC and pressure is at 350 PSI.
Now, open and close the drain very quickly to release some of the pressure. When both the temperature and pressure hit their maximum values again, lower the heat to 0% and wait, as both slowly drop, a vaccuum is formed and both achievements should be unlocked in no time.

The Steam Whistler (CHOO CHOOOO!) and Project Supporter achievements are pretty much self explanatory. For Steam Whistler you literally just have to activate the whistle by pressing the up arrow key when enough pressure has built up, and for Project Supporter you need to click on all of the links to the right of screen.
I'm looking forward for future updates and for what the devs can come up with next.