If possible mark on the sticker what the items are so they can't switch tickets. Have every thing up on tables if possible. Use a carpenter apron for your sales so you don't leave money laying around. Have an extension cord out to try any electric items. Box up a lot of little items you don't want to price individually and mark the price on the box. Have plastic sheets available to cover stuff in case of rain if you are not in the garage. If in the garage, make sure the door to the house is locked.
Put signs out at the corners of your road if allowed. If you do put an add in the paper, be prepared for early birds knocking at the door before you are ready.