Fasting is one of the most effective and yet least practiced of all spiritual disciplines.  I think one of the reasons that we don't often practice fasting is that we don't really understand it.  Campus Crusade for Christ put together a great resource about fasting.  Here you will find out about the different types of fasts, how to start, how long to fast, how to end, and what you can expect.  Take a look over the material and give it a try!  You can find the fasting guide by clicking here.