You probably know as a health club operator that it's easier to keep a customer than to pick up a new one. Your current client base already knows where you are, how you operate, the membership fees and what you generally have to offer to them. Making a switch takes a lot of effort and a disruption in their routine; however this advice is often lost to owners because they're far too focused on expanding business as opposed to keeping it. You don't have to make big gestures or a huge 'thank you' statement, but you should have a general idea of what exactly keeps them coming back into your doors.