Minus RAF, heirlooms, boosting, and frankly "fastest" , I level two teams of five leapfrogging, A: 1-10, B: 1-10, A: 11-20, B:11-20, etc. If you template your macros you can even do random login your non-tanks, which I found to be pretty hilarious at times. But great for getting the edges of the comps working.

Depending on your comp I would any mage in the group to hit 40(?) for the portals.

I use instance timer to gauge the progress of runs, I primarily level in dungeons. Until cata, where you have to basically do the full zone of quests.

If I were just leveling to hit 85 for some pvp characters and perhaps don't have a character that can tank, I would peek at a cata tour guide or similar, and do the choice non-gather quest paths. There might still be a tourguide for boxing, though perhaps it doesn't have cata.

Tourguide what you do anyways.