Don't be a jerk father and over analyze everything they do. Remember you were a child once. Have losts of patience. Protect them above all things, that should be common sense.
Be consistent with them. Structure is huge. Don't go nutso with rules but don't be a push over. You want them to always feel they can come to you so don't put up any walls. Its OK sometimes to be their friend but always be dad first. Remember they are children and prone to stupid mode.
You cannot love them enough.
Congratulations. Your life will change and they will change you for the good.
I love being a father.