Advertise on Craig's List. Make a quick list of some of the items for sale. Mention the street address and the hours. Mention that Early Birds will have to pay double
Have an extension cord set up for those wishing to try out electrical items.
Have store circulars with prices of new items placed next to similar, gently used items, because people love to compare prices.
Make sure you go to the bank the day before and change about $75 into small bills.