The best ways are, get chins from a good breeder that doesn't have genetic malocclusion in any of their breeding lines. Aside from that it's environmental stuff, like making sure your chin is fed a good quality pellet food and unlimited hay. Hay is the only way to naturally wear down the molars so it's very important they eat a good amount (a small handful worth or more) a day. Different hay wears down teeth differently so a variety is good, and keeps it interesting which helps make them want to eat it. Also make sure they have lots of chew toys that they actually chew on, wood and lava rocks, as well as wood sticks to chew. Chewing on things wears down the front teeth. Keeping the teeth worn down helps prevent them running out of room in the mouth and causing malo. The last major cause of malo is injury, so try to prevent any falls or accidents (something I assume you'd be doing anyway ).