IHOP-KC and many other houses of prayer across the nation (and the world) participate in this fast monthly. It's nice to know that thousands are fasting together during these days. They have put together a nice resource on fasting, please read over for more information. For details, refer to<http://goo.gl/erII03>.
As always, it is voluntary, but highly encouraged. There are a variety of ways you can conduct the fast as most of us are marketplace people. Choose something that is doable for you, yet something you can sustain throughout the whole 3 days. You can do a partial fast (not eating a meal or two during a day), partial diet (Daniel fast - eating only vegetables and water), or some other configuration. In any case, fasting is our joy to use to receive more of the Lord. If you are sick or not well physically, fast something that is not food. Creativity is encouraged, but trying to game the system is silly since the fast is mainly for you (and the system is something you chose voluntarily).