Staying power is key to wedding makeup. It needs to go the distance, and be smudge-proof. Start with a makeup primer to prep the skin and make your foundation stay on longer and be true in color. Choose a foundation that is specifically labeled for long-wear, and set it with a loose, translucent powder. Then layer using sheer colors.
Don't forget the waterproof mascara and eyeliner. Even if you aren't normally a crier and you think you won't cry the day of, you just never know. It's better to be safe than smeared!