[TheThinkTank] how do you track shop activity?

Hello, friends.

We've created a shop sign in sheet, which is great for capturing some numbers, like how many people come through the shop during a particular session, how many were volunteers, how many were kids, etc. What I'm having trouble tracking is the number of unique people accessing the shop over a period of time. In other words, I don't know how to factor out repeat participants when I start adding up numbers from session to session. Has anyone developed a good system for tracking shop activity? What kind of information do you ask for on your sign in sheet? Do you have another system, like tagging the bikes and having tags collected when people complete their projects?

Thanks! rachael