I have a 48 hour cancellation policy that I totally enforce and that also included CHANGES to an appointment. That way someone doesn't come for a lip wax and a Brazilian and tell me they only want their lip done when they get there. I have EVERYONE sign off on my policy and they all get a hard copy to take with them. Within that it says that clients who continually move appointments around will not be rebooked since it often results in loss of revenue when it's at the last moment.
I started taking credit card numbers (that go through a Paypal account) if people jerk me around and I charge them.
I've got great policies and they help the business to run since it's just me at LuLu's.
I'm totally not afraid to enforce my policy. I've also fired a few clients over the last ten years that I've been open. I always really think that through though before doing it. LuLu's is a business and it's my income and I take that very seriously. Clients totally know my expectations. In return they can expect that I will run a great business and offer them great services for fair market value.