Hunters are simply the easiest class to level in World of Warcraft. Starting at level 10 you get a pet that will help you kill, keep you free from harm, and die for you so you can escape. You can easily be lazy and simply auto shoot and let your pet do the work while you watch your favorite show. There is only one option for the leveling hunter when it comes to talent tree, and that is Beast Mastery.
This tree will make your pet a true powerhouse, as it is the spec geared towards pet buffs. There is plenty for the hunter as well as many talents improve your shooting speed. The staple talents for Beast Mastery are:
Improved Aspect of the Hawk - Increased attack speed
Focused Fire - Increased damage while pet is alive
Ferocity - Pet critical rate increase
Intimidation - Stun
Bestial Discipline - Increased focus regeneration for your pet
Bestial Wrath/The Beast Within - Damage increase, fear/stun remover
Serpent's Swiftness - Attack speed increase for you and your pet
From there you have a few options. Improved mend pet is handy if you find yourself leveling in areas where your pet will be poisoned or cursed. Spirit Bond gives you and your pet a constant health regeneration effect. Frenzy so your pet attacks much faster after crits.
You should eventually look into getting a few talents from the Marksmanship tree as well. You definitely want Go for the Throat, which gives your pet extra focus every time you crit. That essentially will keep aggro on your pet, even when you find yourself laying down a lot of burst damage.