I agree with the previous two posters wholeheartedly.
My most commonly used skills at level 30 are
Sunder Armor, which is incredible. Even without investing talent points in it, with the second rank you can get the opponent down to -900 armor. Now tell me that isn't beautiful! Rogues will love you. 8P It is also very important in battles against creatures of higher level (4 or more levels higher) since it helps put you and everyone else in your group on a more even playing field with the opponent. Rend, which is so cheap and easy to use, it's like free damage (and, like all DOT's, helps hold aggro, which can be hard for some warrior builds to hold...) Overpower, which a lot of people overlook, thanks to the fact that certain kinds of creatures don't dodge very well (it requires the opponent to dodge first...). For just two talent points, though, you get a very cheap, instant ability that can do positively atrocious amounts of damage and cannot be blocked, dodged, or parried, though it can still miss. ^_^ Demoralizing Shout, which is great crowd control and a fine debuff to boot! Not very handy against casters, though.
For talents, I'm trying to focus on the abilities above when I can. I'm sticking with the Arms line for Mortal Strike, but it sounds like you are a bit more interested in the tank side, which in World of Warcraft is all about using a shield. ^_^
At level 30, my current shield is 661 Armor, and at 60 you'll be looking at shields with as much as 2000 armor on them, and that will make up as much as 40% to 50% of your total AC. So if you're going to be using a shield all the time, you probably want to focus more on the Protection side of the talents. You'll be able to hit the highest level talents of only one of the trees, and for a tank-focused warrior, that tree should probably be Protection.
In that tree...
Anticipation: Very good, even for non-tank warriors.
Concussion Blow: A very, very solid ability to work towards, and the requisite talents for Revenge greatly improve that ability as well.Iron Will: Don't overlook this gem! In PVP, stuns are brutal, and usually spell certain death. Of course, you can always re-spec some points into this near the endgame.Sunder Armor: Sunder Armor is already beautiful, and a bonus to the AC debuff is a real tear-jerker. ^_^Shield Discipline: Like all top-level talents, this is a must as soon as it is available. ^_^