My advice, based on fights against warriors and mages as my mage and my warrior:
Don't fight mages. =D
Okay, seriously now.
Arcane Mages: Seriously, who uses Arcane for damage? XD The only things you ever have to worry about from an Arcane-specced mage are Slow (which can really **** you off if they're Arcane/Frost) and PoM-Pyro (which is something that, as a Warrior, you really, really need to worry about). Try to Intercept as much as you can (most mages will try to get as far away as possible; sometimes you won't even have to back up). Drain all your rage on your best attacks when they're stunned. Either they have Mana Shield up, so you'll drain huge chunks of their mana, or they don't, so you'll drain huge chunks of their health if not the whole bar. Either way, it's a good thing. Of course, they'll try and Nova+Blink once the stun wears off. Stay where you are and either bandage through their inevitable counter-attacks or blast them with a ranged weapon (again, they either lose more mana or health, and if they lose health there's also the small bit of mid-cast stun). Always fear the worst when you're unable to attack effectively (sheep, nova, Slow, etc.).
Fire Mages: You have virtually nothing to fear from them, because Fire-specced mages have neither PoM-Pyro and/or Slow, nor the defenses of Frost. Again, Intercept often. They'll never be able to win if all they're doing is using Nova and Blink and watching their mana bar shrink. Because of the insta-damage spells Fire mages have, and Ignite, Berserker Rage is your friend. Watch out for Impact proccing from Molten Armor. Blazing Speed will annoy you.
Frost: The toughest spec to kill by far. They can trap you, slow you down no matter what you're doing and kite you to the grave, summon Elementals, and all the while remain completely invincible thanks to Ice Barrier (if they have enough mp5 that they can regenerate as much as Ice Barrier costs, or more than its cost, before it runs out, you're in trouble). Frost mages also have the least prep. time of the specs (meaning they can get the good stuff out the fastest). Try to stay in their face as much as you can. Use Hamstring at your first opportunity and chase them; don't always just let them run away and then Intercept. Pummel the spells out of them and Intercept whenever you get a chance. If they put up Ice Barrier, try to break it before 30 seconds pass, because after that they can just cast another whenever they want. You may have to dump a bit of your rage into this but it's worth it. Watch out for Frostbite and Icy Veins. And Cold Snap. And CoC. And Blizzard. And the Elemental. And...you know what, watch out for everything.
If a mage IceBlocks: Either wait, time a Slam or other attacks so it hits right when the effect is up, or run away so you can Intercept them when the effect is up.