Ok I will take a shot even though I do not like Canadians ;>)
So Moneyball was based on using statistical analysis to find undervalued players. What is analogy to gym memberships? If I was a "consultant" I would want to spend my time with prospective clients who were most likely to join and buy some personal training. So lets assume the ideal candidate is someone who buys a long-term membership, buys some personal training, and stops coming to the gym after 2 or 3 months. Do a statistical analysis of characteristics of current and past members who meet these criteria and use this analysis to develop a questionnaire, or some other tool, that will allow you to prescreen potential members so that you can determine whether or not they are worthy of spending time on them or just giving them the quick tour. Prequalifying will allow you to best optimize your limited time.