There's plenty of guides and ways to level and I don't think there's one that is just so superior to others to say "this is the one".
Just adding my own favourite level spot: FFR as well, just East of the Alliance flight point at Brenny Skymoor (forgot the name of the area, it's in the far North)
Reasons for it:
- Easily reachable, even for a lvl90 twink (also for Alliance)
- Easy mobs that can be done with any lvl90 char and don't annoy much
- Lot's of beast and critter enemies, few flyers, constant respawn
My team for it is:
Level pet first for 1 round (should be level 3-4, or Mechanical/Magic)
Lifelike Mechanical Frostboar (2 2 2)
Anubisath Idol (1 1 1) as backup, rarely ever needed
The Frostboar has strong abilities both against Beasts and against Critters, making the fights short, and with "Pig Out" it can heal itself massively on Critters while doing damage, so much that it only drops down in health considerably if you face a few flyers in a row.
As I said, that's just my setup, there's plenty more that are guaranteed as good as this one, worth trying out a few until you find one that suits you on the long run