However, you want to be vague about the specifics of your act until you find out exactly what they have in mind. Never say you can't do something. Maybe they saw something on the most recent TV magic special that they liked. Tell them that is one of the strongest parts of your act, then go buy the trick and do it. Even if they don't tell you till the day before you still have plenty of time to run to the magic store and buy it.
Some magicians list themselves in the phone book or post flyers in laundromats and grocery stores.
I just go to the fast food place during a slow period when the kids are more interested in talking to each other than in the customers. I carry a bag like I have been shopping. Over a period of time, you can hit every fast food place in a twenty mile radius. Now that you have your names you can develop your marketing approach. I use a lot of psychology here again.