When going to restaurants, always paperclip your business card to the tip you are leaving (and please tip well. Tipping 20 percent of the bill is pretty standard now. And if you are alone, leave at least a five). On the back of the card, write something like, "Thank you for such great service. I hope that I can return the favor sometime."
Thumbtack them anywhere you can. A lot of businesses have bulletin boards and walls designed for local advertisements such as flyers and business cards. Tack 2-3 at each place you go - laundromats, diners, supermarkets, grocery stores, etc. The more places the better.
Put magnets on the back of some of your business cards and give them away. Will everyone put it on their fridge? Nope. But a number of people will, and when they have guests over and the conversation goes in the real estate direction, there will be your business card hanging conveniently on the refrigerator.