Christian fasting, what are the rules?

We are to fast to practice self-denial and turning to God to meet all of our needs. I have fasted for 3 days from food and it was very rewarding, but you don't have to do a 3-day fast. Even 1 day or until sunset is good for you. You are "allowed" juices, coffee, chicken broth...any liquid, but that isn't the point. The point is self-denial in favor of turning to God.