Warrior Tips

Rage
The Warrior has a red Rage bar. This is similar to a Mana bar for casters. During combat the Warrior generates Rage based both on damage done and damage taken/prevented. You may also generate Rage using specific abilities. The Rage bar continues to fill as the Warrior fights. Once the Warrior has enough Rage points, the Warrior can use different skills that require Rage. When not in active combat, the Warrior's Rage slowly fades to 0. The Warrior also loses all accumulated Rage if the Warrior switches stances, so plan ahead and avoid changing stances mid fight!
Stances
Warriors have different stances available to them which determine what abilities can be used during combat. There are special stance buttons located above your action bar to switch stances. If you switch stances during battle you lose all your Rage so keep that in mind. Typically you don't switch stances during battle. Stances are for different situations.

Battle Stance is used mainly for soloing, adding different state changing attacks and high damage moves.

Defensive Stance offers fewer types of offensive special attacks but gives the Warrior more defensive specials plus a bonus to your defense rating. This is primarily meant for acting as a group's main tank.
Berserker Stance allows for more critical strikes but the Warrior takes more damage. This is best used when the Warrior is a secondary tank in a party.
Other Information
Warrior abilities that target one or more enemies generate additional threat.
Action Bar
Each stance has its own action bar. You place abilities for that stance on that bar. When you switch stances, your action bar also switches.

Combos
Use a Shield Bash/Block, then attack with Revenge.

Training
It's very important to build up your skills in multiple weapons so you can easily switch to a different weapon if a better weapon of a different type comes along. Keep weapons of as many types as you can in your packs and continue to swap them to build up your skills.

Tips

Team up with healers (Priest, Shaman, Druid) to keep you alive.

Pick one or two of the two-handed weapon types to use.

Manage your Rage! If you are fighting a caster save some for a timely shield bash/Pummel to stop them from blasting you or healing themselves. That one extra use of Heroic Strike may have caused some extra damage but if the monster heals it's like starting all over.

Try and plan your Talents ahead of time.

Protect your group mates. A Priest or a Mage isn't meant to take the brunt of an enemy's attack. Use the Taunt ability to focus the attacks on yourself.
Profession Options
You can pick whatever you want. You might find these more tailored to the Warrior:

Mining/Blacksmithing - Make all your own equipment.
Herbalism/Alchemy - Make healing potions and potion buffs.
First Aid - You can't normally heal yourself so take this skill up to reduce downtime.
Cooking/Fishing - Catch and make food to reduce downtime after combat.