Teach your children how not to become victims.
Teach them to talk to you about anything and everything even if it is uncomfortable for you.
Give them lots of love and attention so they don't need to find love and approval from others outside your family.
Supervise their activities and be as involved as you can be.
Know where they are at all times
Show up at odd times so no-one can ever be sure when you might show up.
Just a few things off the top of my head.