Eh that guys dumb, "I already have guys in full tier0." congrats nub. I recommend doing almost nothing but quests, however you should be running instances once in a while just to get some new gelar. At level 30, go to
http://www.wow-pro.com and follow Jame's Alliance Leveling Guide, it's the best there is. (If you're horde, reroll.
) At around lvl57, you can grind constant scholo/strat for some really good XP, and some good drops. I also recommend grinding scholo/strat for Argent Dawn rep.