Power leveling pets and XP

[Doobjanka]

I started with a level 2 Netherwhelp in The Heartlands with a Cat killing all three pets once the Whelp got a hit in. The different XP values are a mix of level 23's or level 24's.
Level 2 = 418 XP, dinged level 4
Level 4 = 453 XP, dinged level 6
Level 6 = 456 XP, Dinged level 7
Level 7 = 484 XP, dinged level 8
Level 8 = 489 XP, 466 XP, dinged level 9
Level 9 = 466 XP, dinged level 10
Level 10 = 464 XP, 490 XP, dinged level 11
Level 11 = 486 x 2 XP, dinged level 12
Level 12 = 471 XP, dinged level 13
Level 13 = 471 x 3 XP, dinged level 14
Level 14 = 428 XP, 459 XP, dinged level 15
Level 15 = 445 x 3 XP, dinged level 16
Level 16 = 395 x 3 XP, dinged level 17.
Level 17 = 409 X 3 XP, dinged level 18.
Level 18 = 387 x 2 XP, 352 x 2 XP, dinged level 19.
Level 19 = 363 x 5 XP, dinged level 20.

A total of 32 pet battles to get a pet from 2-20.

[Poofah]

I don't have precise numbers, but I tend to level with the daily quests.

I have alts parked at Jaguero Isle, Skulk Rock, and Karazhan for some of the rarer battle pet spawns, which are very close to tamer dailies: Bill Buckler (lvl 11), David Kosse (lvl 15?), and Lydia Accoste (lvl 21). I do these in sequence, it gets a level 1 roughly to 5, 8, then 10. 10 is high enough to survive a hit from a Pandaria tamer pet, so I then do the 7 Pandaria dailies, which is enough to get up to 22 or so. There's several other rare pet spawns that are very close to tamer dailies: Shadowmoon Valley, Searing Gorge, Onyxia's Lair, Argent Tournament, Felwood, Sporeggar, Shattrath/Razorthorn Ridge, possibly others depending on what you're hunting for.

My daily quest team is the lowbie, Darkmoon Zeppelin, and a third pet that can mostly solo each particular tamer. I mostly use Magical Crawdad, with Spawn of Onyxia for the Dread Wastes tamer and Emerald Whelpling for KunLai, Jade Forest and Krasarang. I let the Crawdad/Emerald die late in the fight, then the main purpose of the Zeppelin is to get the last killing blow with Explode so that the lowbie pet gets the entirety of the XP reward, which is roughly 2k per Pandaria daily.

My guess is this takes ~40 minutes of total time, due mostly to the travel in Pandaria. Therefore Doobjanka's method is likely more efficient if you only care about pet leveling, but I'm doing the dailies for the bags anyway, so it's only a little bit of extra effort.

Also, I really want a Netherwhelp...

[Slambert]

My leveling hot-spot is the big tree in Hyjal. Super close to a stablemaster, large variety of endless pets to battle/aquire rares of that are pretty easy to beat, and the mobs are too low level to aggro/annoy me too much while I'm leveling.

My go to level 25 of choice to solo everyone is Lil'XT, tantrum, repair/heal to full, generic shoot once then repeat and all three pets die almost at the same time (including those pesky burrowing rabbits!). Then once I get to level 15-18 with the one I am leveling i am usually able to start soloing all three of the level 21-23 pets for even more xp (probably not until level 20 if the pet your leveling doesn't have a self heal or a damage reduction).