Good luck with that. It's part of the business. Girls and guys both get NCNS. It's a occupational inconvenience as much for provides as it is Hobbiests. It's not like you can take him to small claims court or guys file a grievance with the Better Business Beureu.
Everyone runs their business in a different way... My personal experience is that is better to err on the side of customer service, even if it means less money for you.
Clients will cancel. Sometimes it feels more frequently than others. Besides the obvious difficulties of collecting a cancellation fee, a client is much more likely to book with you again if he did not have an unpleasant experience while dealing with you. Setting a charge for when/if they decide to reschedule may make them resent you and look somewhere else.
Screening them properly (looking through the forum to see if they are reported "timewasters"), maintaining a helpful attitude, and giving them something to look forward to will help decrease your last minute cancellations.
Maybe I should try charging the girls that NCNS me a fee...... Probably wont ever hear from them again like the few I tried to help out a couple of times and went poof. Eh -- Lesson learned.