How to NOT get a Maskutchi.
Don't let the hearts fall below 2
High dicipline level.... you should have atleast 6/9, or 7/9 when it's a teen. Then it will evolve in to a good character, like Mimitchi
Don't feed it snacks.
Also, connecting and being best friends with a better character can affect the growth of your tama. So make friends with good characters
If you mate with a good character- eg. Mimitchi or Mametchi, the chances are the next tama will evolve into a good character!