Torchlight 2's punchiest class, the Berserker is all about melee weapons and fast and frantic combat. She's a scrappy brawler: the Berserker skill trees have less area of effect attacks than the other classes, so kills are made by quickly bouncing between one-on-one encounters, filling the charge bar to unleash a frenzied flurry of critical hits.
The thing to remember when starting out as a Berserker is that it's not a tanking class. Your starting Vitality (which determines armour and HP) is dangerously low, and if you get too absorbed by the hypnotically visceral combat momentum, it's all too easy to end up in danger. There are a few skills that do wonders for your survivability, but these restrict your weapon choice more than the Embermage. Your best bet is dual-wielding fast hitting melee weapons, and keeping your Strength and Dexterity high to increase your high-damage critical hits.
All your skills take the form of a wolf-spirit working through your fists. The starting one, Eviscerate, is a good, hard-hitting swipe of damage, but you're better off prioritising the skills that support your standard melee attacks. Primarily this means Frost Breath, which has a high chance of immobilising enemies directly in front of you and, more importantly, softens them up for increased weapon damage. Get into the habit of blasting this out at the start of every encounter.
Another early skill to grab is Shadow Burst, which sees you lunge through enemies, damaging them but also healing yourself. The HP gain isn't miraculous, but periodically using it in fights will help to increase your overall survivability. Combine it with the passive skill Blood Hunger, which gives back a percentage of health for every critical hit, and you'll find it a lot easier to regulate your HP bar without constantly chugging potions.
When you hit level 7, get the Stormclaw skill immediately. It not only gives your melee attacks extra electrical damage, but can also generate a lightning bolt that hits additional enemies. When activated it lasts 40 seconds, but only has a cooldown time of 20. Basically, if you're having a fight, you should have this active.
Elsewhere on the skill tree, Wolf Shade summons a ghostly familiar to run off and cause havoc, making it handy in boss fights or against large groups of enemies. For pure boss ownage, however, you'll struggle to beat the level 14 skill Raze. It's a powerful uppercut attack that increases in damage with every successive hit. Just find something tough, and spam it until they fall over.
Fill the charge bar and the Berserker enters Frenzy, dramatically increasing her speed and guaranteeing insta-gibbing critical hits on her melee strikes. It's an agonisingly short power, lasting only six seconds by default, so when activated, forget about everything and just find some more monsters to punch. You can always go back for the loot. Where possible, put spare points into Frenzy Mastery, a passive skill which increases your frenzy time by half a second per point. It's not much, but you'll appreciate every extra swipe.