This guide will show you the absolute fastest way to get to level 49, but only good for the alliance as they are the only ones that can do this quest.
When you hit level 40 head off to the Hinterlands to the Wildhammer Keep and talk to Fraggar Thundermantle to get the Troll Necklace Bounty quest. The best part about this quest is that it is repeatable, meaning you can do it over and over again. Granted the exp reward does drop after the initial turn in but an extra 390 exp while grinding always helps!
After you get this quest you will want to head east to Zun'watha. At that location you will find a camp of trolls. Start on one side and just go in a circle killing all the trolls. They have a fast respawn rate so when you get around the camp once they will be respawned so you don't have to stop!
Using a hunter I found out I was using a lot of mana so you might want to conserve mana when you can to keep going so you will not have to stop a whole lot. Don't worry you will stop a few times when first doing this but it gets easier and better as you go.
Back to the Troll Necklace Bounty quest, usually you can get 1 necklace for every 2 kills it seems. They drop pretty easily and you can end up with 100+ after an hour of grinding here. The best part is to turn in the quest for exp you only need 5. First time you turn in the quest you get 3900 exp points and everytime after that you get 390 exp.
So, anyway off the trolls you get 250-300 exp per kill and they are easy kills. At 100 you can turn in the quest 20 times for an extra 7800 exp points.
In my opinion, where else can you get an extra 7800 exp points an hour at level 40-49? Also, sometimes you can find the necklaces on the auction house also! How simple to get a lot of experience really quickly!
