Leveling is something that not many people get excited about while playing World of Warcraft. So follow this Alliance leveling guide, and hopefully you'll be at level 80 before you really dread leveling a new character.
As with any Alliance class, run through the quests in your starting zone as quick as possible, this is the easiest way to get to level 12 fast. Next, make your way to Westfall (Night Elves can get a port to Stormwind to get there quickest), and quest through there. After you've done those, make your way over to Redridge Mountains, where you can quest all the way up to level 25.
After level 25, head up to Wetlands, as this is probably the best place to try and quest. Then, you only have a quick run up to Arathi Highlands at about level 30, where you can pull in quests there to get up to level 37. From levels 37-41, Stranglethorn Vale has the best quests. There are a bunch of chains that you can do to run through that area as quick as possible.
Levels 40-50, go to Tanaris first to do those quests, and then as you complete them, they'll lead you up to Hinterlands. Hinterlands some good quests for experience points as well. You'll find the most quests after level 50 in Un'Goro Crater. The place is loaded with quests that you can stack and knock out 50k exp in an hour.
Around level 55, you can go up to Silithus. At the Cenarion Hold there are a few quests, but you might have to go up to Winterspring to complete hitting 59 before Outlands.
Hitting level 59 before Outlands is a good idea. There are a lot of quests in Outlands, but you may run through too many of them before you get the chance to level. Try and wait as long as you can before you make your jump through the portal. Once you are past level 60, then your job becomes a lot easier because there are lots of daily quests you can do to help you leveling to 80.