now grab the pet you want to level, put it first on your team. find a pandaria pet battle. use one single skill with this pet (it doesn't matter if it misses). this is important: don't let your level 1 pet die. it's kind of luck dependent at level 1 because most level 23 pets can one shot level ones, so you'll have to be lucky enough for them to use a non damaging skill. after using one skill with your level 1 pet, change to your main pet and destroy the enemy team.
your level 1 pet will get half of the experience. watch her skip from level 1 to level 4 in one fight. reach level 25 within one hour. repeat for all the other pets you wish to level up