Repetition, repetition and.... repetition. BUT, BUT, BUT it must be reinforced by them seeing you live out what you teach. They will model their lives on the example set before them (good or bad), and they are watching you even when you are not watching yourself.
I heard a story about a father who was playing some hockey in his basement with his two sons. The dad was left handed and his sons were right handed. After playing for a little while, the dad realized that his 4 year old had switched hands to play left handed like his dad albeit not his natural way of doing things. The moral is that kids will copy their parents, so set forth good habits and values for them to imitate.