I've found that the best hunter leveling spec in WotLK is still Beast Mastery. The reason for this is that you can maintain your range from mobs/enemies, while your pet holds aggro and does damage.
With this spec I would highly recommend getting a good tanking pet such as a boar or bear, when you get to level 32 or 33 I would switch to a gorilla (these are the best pets for tanking as they have AoE attacks for holding aggro and do a lot of damage overall).
The other thing to remember is that your pet will be doing a lot of damage for you, so begin your rotations with Aspect of the Hawk, then switch to Aspect of the Viper to regen mana while you finish the mob off.
If you're looking for a great leveling guide, check out this Zygor Guide Review
Enough with the background, let's get to the best hunter leveling spec:
Levels 10-14
5/5 Lethal Shots (I know this is in the Marksmen tree, but 5% extra crit chance is great... after this we're in the Beast Mastery Tree)
Levels 15-19
5/5 Endurance Training
Levels 20-22
3/3 Thick Hide
Levels 23-24
2/2 Focused Fire
Level 25
1/1 Aspect Mastery
Levels 26-30
5/5 Unleashed Fury
Levels 31-35
5/5 Ferocity
Level 36
Initimidation
Levels 37-38
2/2 Bestial Discipline
Levels 39-40
2/2 Spirit Bond
Levels 41-44
4/5 Frenzy
Level 45
1/1 Bestial Wrath
Level 46
5/5 Frenzy
Levels 47-48
2/2 Improved Mend Pet
Levels 49-50
2/2 Animal Handler
Levels 51-54
4/5 Serpent's Swiftness
Level 55
1/1 The Beast Within
Level 56
5/5 Serpent's Swiftness
Levels 57-59
3/3 Ferocious Inspiration
Levels 60-64
5/5 Kindred Spirits
Level 65
1/1 Beast Mastery (4 extra skill points that you can use in your pet's talent tree. Some people think it's a waste, but I think it's great since you're very reliant on your pet with this spec)
At this point I switch back to the Marksmen tree
Levels 66-70
5/5 Mortal Shots
Level 71
1/1 Aimed Shot
Levels 72-74
3/3 Improved Hunter's Mark
Levels 75-76
2/2 Go for the Throat
Levels 77-79
3/3 Improved Arcane Shot
Level 80
Time to respec for your raiding or PvP needs!
At 80 it's time to start running your daily quests and focusing on what you want with the end game. If you're looking for a great guide on Daily Quests check out this Dugi's Daily Guide Review
