Make sure everything is marked.
When marking clothing, make sure to include the SIZE of the clothing on the tag with price so people don't have to try to find the size. If it is a name brand, include that as well......some people look for name brand clothing.
Hang up ALL clothing if possible. Some people don't like looking through a mound of clothes thrown on a table.
Make sure your sale is in a building, like a garage, if at all possible.
Make sure to have a sign showing people where the sale is located. If you don't want people to park certain places, make sure you cord them off somehow. We use orange road construction cones.
Make sure you go to the bank the day before and get $100 worth of change: Get like two $10 bills, four $5 bills, forty-three $1 bills, one roll quarters ($10), one roll dimes ($5), one roll nickels ($2),......something like that so that you will be prepared to make change. They make those lock boxes that have like the black money holder piece.
Definitely make it a combo rummage & bake sale.....sell drinks, have low music playing, etc.