Levels 21-30 are fairly straightforward although they do culminate in an awesome prize in the name of Feign Death (and these days, a mount.) Let's see what sort of goodies you'll get:
Scorpid Sting is what you will learn at level 22. This reduces a target's chance to hit by 5% for several seconds. Not really as useful as Serpent Sting in early-level grinding, but your friendly neighborhood tanks and healers love it on boss fights in instances and raids. Just remember to keep it "refreshed".
Beast Lore, ah, Beast Lore is great. You learn it at level 24 and will show you information about any beast in the game; its armor, hit points, the amount of damage it does, and (most importantly) whether or not said beast is tamable and if so, what moves it teaches and what foods it eats.
It has occurred to me that we have not yet talked about taming pets for skills. Basically, you will want to continually update your pets skills and the ranks of their skills as you level. You can learn some abilities from the hunter trainer, but others you have to go out and "find" in the wild. Once you find a pet with the skill you want, you tame it (be sure to put your previous pet in the stable first), feed it and teach it growl-- and then go out and fight with it. After a time, when it uses its special ability, you will get the message "You have learned a new skill: [Pet Skill and Rank]" in your text box, which means you are now free to teach it to pets who are able to learn it.
At level 24 you also learn Track Hidden. Track Hidden does not work quite like the other tracking spells; as in it isn't going to put every rogue or stealthed mob on your mini map (that would be nice, but alas, it doesn't happen.) What it does is increase your stealth detection and puts mobs that you detect on your minimap. This is a handy tracking spell for quests with lots of stealthed mobs (such as those prowling panthers in Stranglethorn Vale) and also in PvP if you think there might be a rogue or druid close by.
At level 26 you learn Track Elementals, which works like most other tracking spells against anything that says Elemental on the tooltip.
Level 26 is also when you get Rapid Fire. Rapid Fire is good for: emergencies when solo'ing when you have to get something down fast (be sure your pet has a solid hold on threat), boss fights when you want to unleash the DPS, and PvP to get an edge vs., say, other hunters. Post-Steady-Shot hunters, you will have to be on your toes to continue a shot rotation while under the effects of Rapid Fire but it's certainly not impossible to manually-weave one in there.
You learn Frost Trap at level 28. It's good for escaping mobs that you'd rather not fight (or that overwhelmed you), and it's really good in PvP. Put one at a choke point in AV (such as on the bridge), or my favorite: put one at the entrance to the tunnel right before your flag-carrying teammate runs in. All those guys hot on his tail? Yep, derailed.
This trap is also good for kiting guys around whether in PvP or PvE, though for the most part I found that I mostly just need Wing Clip/Concussive Shot.
And then you hit level 30! Grats on your mount, firstly. (back in my day I had to walk through Stranglethorn Vale, uphill both ways! /shakes cane)
Aspect of the Beast is the newest Aspect to welcome to your stable and I'm sad to say it's not particularly useful. It is a pure PvP Aspect-- it makes it so other classes with tracking abilities cannot track you-- and I've used it once or twice in Warsong Gulch when going for the flag (or defending it), or on PvP servers in hotly contested areas... but for the most part I don't find it to be worth it. Your mileage may vary.
Much more importantly, you learn Feign Death, which is your lifeline when it comes to dropping aggro. Use it when you have aggro, use it when you don't have aggro yet but are getting there, and use it to get people (and pets) to stop targeting you in PvP. Use it and learn to love it. You can read much more about the mechanics of Feign Death at my post about it here.
If you are leveling pure Beast Master you will learn Intimidation here, which is handy for stunning people in PvP, and for helping your pet to establish aggro when out questing. Marksman hunters will likely be putting their point here into Scattershot which is great for getting back into range (especially in PvP). Survival gets Counterattack but in all honesty I have never used this move so I can't tell you much about it. I hear it is useful in PvP.
Mmm, learning more and more hunter stuff all the time. Tastes yummy, doesn't it? We're cooking up some more, too, and it smells delicious. But that'll wrap us up for this week.
In case you are new to the series, here's where we're at thus far:
So You Want to Play a Hunter?
Part One: Introduction & The Birth of a Hunter
Part Two: Just Starting Out & Levels 1-5
Part Three: Levels 6-10 and Jump Shot Kiting
Part Four: Talent Points & Pets
Part Five: Life With a Pet
Part Six: Levels 12-20
Part Seven: Intro to Freezing Trap
Part Eight: Levels 21-30 [Current]
Until next time, go pamper your pet.