How to go about finding Models?

I have some conceptual ideas that I want to try in my photography. I am not a pro and cannot pay for professional models (would prefer more "normal" looking people anyway). I actually have a pretty specific type I'm looking for. How would you go about finding models and how would you approach them to sit for you without monetary compensation. Is it appropriate to offer them digital copies of a few of their favorite shots? Do you just approach them on the street or (eek!) post a craigslist ad? Anyone who has done something like this, I would appreciate if you would share what worked and what didn't. Thanks for your time.