To fast means to not eat. To pray means to commune with God. To fast and pray for an extended period of time means to go several days without eating and spending as much time as possible in prayer. There is no special biblical way to do this other than to just do it. It is good for you. We recommend that all believers do so on a regular basis. It will be necessary to drink some kind of liquid during this time if you go very long. Drinking a liquid is not breaking the fast (a milk shake might be going too far!).