After each level, and before the beginning of the next level, get to the upper left-hand side of the screen (where balthezaar enters each level) the pet-pets will stay away from that area and will therefore be harder for balthazaar to get.

 

For the game, Extreme Herder, get the snowflakes ASAP, as they freeze the wolf guy right where he is which gives you more time.

 

If you need to take a short break, get all the petpets in the pen EXCEPT ONE. As soon as you pick up that last petpet, Balthazar will return to the corner and stay there as ong as you keep holding the petpet.