I personally just play like I would solo...I quest my way up(grinding + no tangent game goal = no fun/boring) and run instances around the right level, maybe get some gear out of it(SM in particular's the only one I'll re-run because it's such a good instance with good gear and exp, boxing or not; ZF was nice for the spelldmg cane though); I just can't stand to, or bring myself to, grind mobs purely for exp. I'll scrounge for green/red quests instead or run an instance till I get more quests lol

So far it's proven to work though...Warr/Druid = 21 days /played to 60, Rogue = 18days /played to 60, Hunter = 14days /played to 60...I forget how long I had when I hit 70 on the latter 3. Either way may Boomkins are sitting on 10-11days /played at 67. Followed the exact same lvling paths and methods I always have, the 2.3 exp change makes a huge difference as does perma-grouping.

It boils down to, "How patient are you?"; "fastest" can be incredibly boring despite it's effectiveness. I dunno about the rest of you guys but I play to have fun; I play normally and get there eventually regardless, and have fun doing so, no rush yo, no rush :P