Hey LckyGrl25... one of the things I would recommend is that you offer some type of Free Health Report or Health Tip sheet -- something with perceived value -- to the people at the health fair. Then, ask for the contact information of the people who come over to request the free "widget". What this does for you is build a list of warmer prospective clients that you can market to after the health fair.
Even better, have several different free reports to offer, each one for a different target audience. Then, when they request a certain free report, have them put their contact information on that free report's sign up list, and now you have a highly targeted list of people to follow-up with later on. This way, you can make specific offers to those people who requested certain reports.
let me know how it goes,
Todd Brown