The secret to a successful yard sale is foot traffic. The more folks who walk through your sale, the more you'll sell. Lots of cars parked on your street tell yard-sale cruisers where to find you. If business is brisk, buyers won't leave your premises without that lighted beer sign, for fear that someone else will snatch it right up. Do spring a few dollars for a newspaper ad.
Many local papers offer special garage sale rates, or free signs to yard sale advertisers.
Use neon posterboard and deep-black markers. If you can't see your signs from a block away, neither can your customers. If you live tucked deep in a twisted spiral of subdivision streets, place sign at each and every corner between your house and the nearest main road. Make it easy for buyers to find you. Prep and price.