Open mics are best done at a time when its otherwise hard to get customers into the place. Such as a Monday or Tuesday evening. If you can develop a successful open mic with a good variety of performers coming in regularly and bringing their family and friends, you end up filling the coffee house/muffin joint/juice bar with paying customers without having to pay a whole lot for a big name entertainer. Open mics are lots of fun for the regulars who come in week after week, and they provide a great venue for newbies to polish their performance in a friendly, supportive environment. If you already have a "KILLER" open mic going on somewhere else in the same town, I would pick a different day and hope to pull some of the same "KILLER" crowd in to yours. Good luck,

Mike