Love. Love is a decision as much as it's a feeling; you decide to do it and every day remind yourself. Love is unconditional and never-ending. Love your wife and children and even yourself.
Don't expect perfection either in yourself or others. We Dads screw up all the time. Expect it and get over it and be just as forgiving in others.
Set an example. Actions speak much louder than words. We all want our kids to be better than we are but why not use them as a reason to be better.
Realize your kids have minds of their own. We show them the way but sometimes they are just going to do their own thing.
Use both positive and negative reenforcement but be slow to anger and quick to praise. Remember the power you hold in your child's life and use it carefully.
Explain why doing things is good or bad and be open to discussion. Even young children will begin to understand and make their own decisions wisely. And it'll force you to think about if you're being reasonable or just saying "because I said so!"
Do everything with a smile and a song. Why fight when you can make everything a game. A positive attitude and some fun can work miracles.
Please, thank you, sorry. Be polite. Even when talking to your kids. They will mirror your behavior. If you overreact explain what you did wrong and apologize.
Have a sense of humor. Sometimes you have to laugh or cry at situations. Just laugh.