Best way to take out some of the guesswork and or waste is to run them one or two days a week as a special. Limits your chances for having extra product down to one or two days until you get a clientele built.
Allow customers to pre order for your "rib days", and cook a little less than you think - Quality over quantity. Nothing wrong with running out of a good thing, and creating a little scarcity. It's a good marketing ploy, and folks will get there early next time to make sure they get their ribs.