A werewolf and a vampire differ incredibly. Werewolves are rarer, and being attacked by a werewolf does not give you lycanthropy. Of course, there are a lot more differences than that, and they shall be covered later as appropriate.

Instead, then, you'll need to deliberately become one. This is easiest if you're playing a Warrior-style character, but works with any archetype. Partway through the Companions questline, you're accepted as a full member of the Companions, and are toasted into their numbers. However, upon completing the quest Proving Honour, you're invited into the Companion's Circle. Should you accept this invitation, you'll be taken into the Underforge at night and undergo a ritual to become one of Hircine's Hounds. You may want to go on a little rampage immediately afterwards, to get used to the new mechanics.

As a werewolf, you essentially become a dual-wielding bezerker. Left and Right attacks are effectively the same, but holding for a Power Attack unleashes a combo, as opposed to the single strong strike. Using both "weapons" at once will strike with a backhanded fist, knocking enemies away and ragdolling them - comparable to using all three words of Unrelenting Force, but with less knockback. In addition to this switch-up, you'll get several unique finishers that knock your target to the ground and, well, devour them. However, you lose the ability to regenerate health naturally. Any buffs placed on you, such as Stoneflesh, will carry over to your werewolf form, but can't be recast until you return to your normal form. You can't bring up your inventory as a werewolf, but your carrying limit becomes 1,900. This can come in handy for magicians that are overburdened.

Killing a humanoid enemy - be it man or mer - gives you the option to feed on their body by standing over them, pointing the cursor at them and pressing Use (default E). Doing so heals you a significant amount, and also extends the amount of time you can sustain your form by 30 seconds. It's quite easy to bounce from one victim to the next like a hairy pinball, should you be able to keep the kills up.

There are ups and downs to everything, and lycanthropy is no different. I'll talk through all the advantages and disadvantages of each, with my thoughts on the matter included.

• Werewolves are faster. This is useful for chasing down prey or retreating from a dangerous situation alike - just don't transform exclusively for the latter, as the odds are you won't make it through the transformation. The sprint, in particular, sees you gallop fast enough to catch an elk.
  
• Werewolves are stronger. As well as the previously-mentioned 1,900 carry weight, a werewolf's attacks are ruthless. I'm currently using a Legendary-grade Daedric War Axe with a Fire enchantment (not the best enchantment) and I'm still taking enemies down faster as the werewolf. This might be because of my perks (See Dawnguard Additions, below) but even without them they'd come to about the same speed.
  
• Werewolves are hardy. Gaining the beast's blood increases disease resistance to 99.9% - except for Sanguine Vampiris, to which you become fully immune. No more Witbane or Rockjoint!
  
• Werewolves can howl. Okay, so it's not a Dragon Shout, but the werewolf's howl is a powerful weapon if used right. See below for details on the howls.

• Werewolves cannot rest. Even in your non-Beast form, you lose the resting bonuses (which grant bonus experience towards any skill for a while after resting in a bed). I haven't noticed it much since I went straight for werewolf, but it has slowed my game down a little compared to other characters.
  
• Werewolves cannot be vampires. The two are mutually exclusive; as well as granting immunity to Sanguine Vampiris, lycanthropy overwrites existing vampires. It can be useful if you want a cure and can't find a Black Soul Gem for Falion, but most Dragonborn vampires become a vampire willingly. However, this brings up a problem for those with the Dawnguard expansion pack - see below for details.
  
• Werewolves cannot loot. I brushed over this before, but the inventory is entirely locked out of use. You can't use anything from it - so no potions, no weapons, no armour - and you can't add to it by looting. You can't even lockpick locked doors! To make matters worse, some dungeons have cobwebs that must be slashed through - werewolf claws do not count as a weapon that can cut them.
  
• Werewolves cannot regenerate. An injured werewolf in Beast form will remain injured until they feast on the corpses of their victims. Be careful if taking an off-road path to your next hunting ground, as cliffs can prove very dangerous.
  
• Werewolves are larger. As well as the obvious implications regarding arrows and knees, this also means that smaller dungeons can be a bit of a problem. A strange fix is to go through such tight spaces backwards, although this isn't foolproof.
  
• Werewolves terrify innocents. Okay, this one's a given, but most people that are usually friendly will attack you on sight. Notable exceptions include followers, Companions that are aware of your lycanthropy and (sometimes) the army of your choice. In addition, transforming when someone can see you incurs an immediate 1,000 gold bounty in whatever hold happens to be your hunting grounds. An easy way to get the Master Criminal achievement, maybe, but still a problem to work with, especially early game.
  
• Werewolves are limited. Unless you get the Ring of Hircine, you can only use your Beast Form power once every 24 hours, same as any power. If you're a powerful werewolf you can feed long enough to tick the time over, but it's still an annoying restriction.
  
• Werewolves have no range. More a limitation than an outright weakness, I thought it important to mention that it's impossible to hurt a target from a distance, although your howls may still prove effective.
  
• Werewolves are loud. Good luck trying to sneak in Beast form; you can't. It's simply not an option.
  
• Werewolves can't relax. Once you've turned into a werewolf, you're stuck in the form until the timer runs out. It's easy to say "Well, why not stop eating?" That's like asking why health is so useful; in the middle of a battle, the more eating you do the longer you live. Unfortunately, if you need to shift out of being a werewolf - be that for a locked door or looting the last chest - all you can do is wait.

As well as its terrifying visage and ruthless strength, the werewolf can utilise a supernatural howl to achieve several effects during combat.

The newly-turned werewolf can only utilise the Howl of Terror. After a short breath, the werewolf roars his rage and bloodlust for all to hear, terrifying those of a weaker will. Enemies up to level 25 will be treated as Feared - although this doesn't work on the undead, nor on dwemer machines.

Talking to Aela the Huntress can reveal she's looking for more Totems of Hircine to expand your options. These are Radiant quests, so won't always turn up, but keep trying and she'll eventually guide you to a dungeon. Clear the dungeon to loot the totem. These totems will be returned to the Underforge, where they can be used to change the werewolf's roar's ability. The first such totem, the Totem of the Hunt, grants the Scent of Blood ability. Replacing the Howl of Terror, the werewolf roars to focus itself and hone its senses to unnaturally high levels. This acts as the spell Detect Life, complete with its limitations, but can be "cast" as many times as you like, in rapid succession - although the roar does attract the attention of anybody nearby.

Aela's second quest has you search for the Totem of Brotherhood. Once you've found, returned and used it, you gain the Howl of the Pack, which replaces your current Howl. The werewolf roars once again, but this time reaches to the Hunting Grounds of Hircine and brings forth lupine spirits to fight by the werewolf's side. Two wolves will be summoned to your side when you use this Howl, but they exist for a limited time - and you cannot Howl again until that time expires, even if the wolves die first. The third quest Aela offers you has you find the Totem of Fear, which allows the werewolf to use the Howl of Terror again.

The Daedric Prince Hircine, Huntsman of the Princes and Father of Manbeasts, is the patron "saint" of werewolves, and will look kindly upon any who hunt in his name. Although the main villain of Bloodmoon back in the third Elder Scrolls, he's quite helpful for werewolves, as one of the two artifacts he offers is his Ring, which allows unlimited transformations by using it instead of the Beast Form power. Equipping the Ring grants the power; likewise, taking the ring off removes the use of its power. There're other walkthroughs of the Daedric quests online (an example can be found here[elderscrolls.wikia.com]), so I'll just go through the basics.

• The quest can be accepted at any level.
  
• Go to Falkreath Jail and talk to Sinding, the prisoner stood in a well. You'll be given a cursed variant of the ring you want, which will randomly trigger your transformations - even if you aren't a werewolf.
  
• Hunt for the stag Sinding mentions and slay it.
  
• Track your new quarry down to Bloated Man's Grotto
  
• You'll be given a choice to hunt or save your quarry. For the (uncursed) Ring, you want to save it; killing it has Hircine grant you the Saviour's Hide, which we don't want (despite its attractive 15% magic and 50% poison resistances)

That concludes the basic guide; however, the two larger DLC packs, Dawnguard and Dragonborn, add something new to the table. They'll get their own sections below.

Given the focus on vampirism, you wouldn't think the Dawnguard DLC pack offers a lot for the werewolf. And that's where you'd be wrong; Dawnguard offers a huge improvement to the werewolf in the form of perks! As a werewolf, hitting your character menu button (default key Tab) will bring up the werewolf skill tree. Look familiar? Perk progress is made by devouring the flesh of your fallen enemies. As a general rule; if its soul can only be captured by a Black Soul Gem, it'll add to your perk progress.

• The first perk is simply Bestial Strength, which increases the damage you deal as a werewolf by 25%. This can go up to four times, for a grand total of double the normal damage.
  
• The leftmost branch improves the Howl of the Pack. The lower one, Totem of Ice Brothers, replaces the two wolves you summon with the stronger Ice Wolves. The higher one, Totem of the Moon, needs the Ice Brothers perk before letting you summon two spiritual werewolves to fight by your side! They can't howl and don't have any perks, but still, werewolves! Now you can be the alpha wolf!
  
• The second branch from the left is simply Totem of the Predator. It increases the range and potency of Scent of Blood; as well as detecting living enemies, it also tells you if they're idle, looking for someone or actively in combat through different colours.
  
• The third branch is the Totem of Terror, which simply increases the range of enemies your Howl of Terror can affect. A simple upgrade, but it can make the difference between scaring a Giant and not scaring a Giant.
  
• The final branch affects the werewolf themselves, and is a good starting point for werewolves everywhere. The first perk is Animal Vigor, which grants a whopping 100 points to both Health and Stamina while in beast form. Useful at any level, since getting that much health and stamina would take 20 levels of normal gameplay. The second skill is Gorging, which heals you for twice as much health as before when eating a body - useful if you pause for a quick feast. The final perk, and arguably one of the strongest, is Savage Feeding, which lifts the ban on eating non-humanoid meats. Undead, dragons, dwemer machines and Spriggans become the only thing I've noticed you can't eat; everything else can be eaten. The only problem is, eating non-humanoid meats only adds half of the bonus time.

Although I haven't tested it myself, apparently being cured of your lycanthropy for the first time does NOT undo your perk progress, it just stops you from adding to it until you regain lycanthropy.

A Dawnguard player also has two unique opportunities to be cured of lycanthropy, although you gain vampirism in exchange. The first instance is when Harkon offers to turn you into a Vampire Lord; accepting cures you of lycanthropy. Should you pass that up, the second and final opportunity is the first time you enter the Soul Cairn, as one of the options will turn you into a vampire - again, overwriting your lycanthropy. Even if you don't take these two options, don't fret, as there is a way to cure yourself even in the DLC-less game. It should be noted that it is possible to return to being a werewolf if either of these methods are taken by talking to Aela, although this is a one-off.

The Dragonborn DLC pack doesn't offer much to the werewolf player; however, four new rings are introduced. Sadly, you can't use these rings with your well-earned Ring of Hircine, since they occupy the same slot, but the money they cost will force at least a mid-game level of progress so you'll have some sort of solution.

On the island of Solstheim is a small outcrop known as Frostmoon Crag. Beneath it lies a small pack of werewolves posing as hunters. Although distrusting to non-werewolves, they will welcome fellow werewolves with open arms, even offering to trade with them. The leader of this pack, Majni, sells four powerful rings that have been blessed by Hircine, each offering four distinct power-ups for your bestial form.
The first, the Ring of Bloodlust, increases the damage you deal as a werewolf by a staggering 50%. However, it also increases the damage you take by the same amount, so caution is essential with this ring.
The second, the Ring of Instinct, acts as the Slow Time shout for twenty seconds. Time slows for everything, including you, but you aren't as effected by the slowdown. This lets you move faster and react "quicker" than before.
The third, the Ring of the Hunt, allows the werewolf's health to naturally regenerate over time. Typically, this function is denied to the werewolf, so this ring can come in handy for the time you spend passing between hunting grounds dungeons.
The final ring, the Ring of the Moon, increases the duration of a Howl's effects by 25%. Unfortunately, this either has no effect on the Howl of the Pack, or also increases its cooldown.

If you can't find the Crag yourself, ask for rumours at the Wretching Netch. This sort of story tends to drift around, after all.

So you've had your fun as a werewolf, but you've decided that the large numbers of downsides to being a werewolf render it no longer worthwhile. Alternatively, you were turned by accident during the Companions' questline, and want to cure yourself of this blight. Don't worry, there's a way to do it - in fact, you already know a bit about it if you've done the entire Companions main questline.

First, know what you'll miss out. Lycanthropy is a once-in-a-lifetime opportunity; curing yourself of it will mean you'll never be able to return to being a werewolf. You'll also be denied access to the Underforge, and the second exit from Whiterun with it. ... that's about it.

Asking any of the Circle for jobs, with exclusion of Aela, will sometimes bring up the offer of curing yourself of lycanthropy. It's explained pretty well in game, but I'll add a basic description here.
You'll be asked to obtain a second head of the Witches that first cursed the Circle to lycanthropy if you don't already have one. Once you've done that, take it down Ysgramor's tomb and burn it, as you did with Kodlak. As with Kodlak, the spirit of the wolf that's possessing your body will come out and fight you. Beat this spirit to be cured of lycanthropy.

There is an alternate method for those who have the Dawnguard DLC, but that's covered under the appropriate section and won't be repeated here.

Hopefully, you've read through this guide and now have a good idea of what it means to be a werewolf. May Hircine guide your fangs to their prey, and may the Vigilants of Stendarr fall before you! Glory to Hircine! Glory to the hunt!