Re advertising: If your local store have bulletin boards, put signs up there. Be sure to say it is a Garage Sale for MD.
If you have regional advertising papers, those are very good. I get my best customers from out of town. One of our advertisers gives you free signs when you place an ad.
Good signs are important. Put a couple on the nearest busy road. Many will stop because they see the sign.
Also, in front of my house I set up a step ladder with balloons attached and a garage sale sign. It draws attention.
Re pricing: It depends on the market in your area. I notice a big difference in larger cities. The prices are higher there. Small towns are usually cheaper.