If you win just one battle against a high level pet (approx. lvl 20) your level one
pet will jump up 4 levels each win for the 1st two wins.
But how to win a battle without your level 1 pet getting one-shotted?
Simple, bring a bear. Any bear will do, and it doesn't need to be high level, it only needs to have enough health to be able to take one hit itself, and high enough to have "Bash". (I use the Infested Bear Cub because it gets "Bash" at level 2, which means you get to level two pets together if you're still leveling an Infested Bear Cub. The Darkshore Cub doesn't get Bash until level 15. And the Anodized Robo Cub doesn't have "Bash". Baby Blizzard Bear also has Bash at level 2, if you have one.)
(Warning: This doesn't work against critters because critters break free from stuns. Also if the enemy evades your bash, or bash misses, you will have to forfeit and reengage.)Make up your team:
A bear; Your level one pet; and your level 25 pet (I prefer the Emerald Proto-Whelp because his two healing abilities, combined with "Breath", can take down a whole team of lvl 25s in the wild).Technique:
1) The bear goes first. Hit the enemy pet with "Bash".
2) Immediately bring out your level one pet, then immediately switch to your level 25 pet. Provided the pet you "bashed" is anything other than a critter, it will sleep through the pet-swap, and your level one pet will suffer zero damage.
3) Mop up the rest of the team with your level 25 pet.
In two wins your pet will be level 6 (maybe level 5). Do this with all your level one pets, swapping them for new level one pets every time one reaches level 6. Then put together teams of two level 6 pets, hitting, then swapping, and cleaning up with your level 25, doing this until all pets are level 10 to 15. When all pets have reached level 10 or 15, head to Pandaria and finishing leveling there.
The Emerald Proto Whelp will heal and kill through a full team of level 25 wild pets.
I hope someone finds this little guide useful.