This Instructable will help you to have your own profitable, organized and successful garage sale. It's fun (you meet great people) but it IS a lot of work, making the maximum amount of money possible at your sale will make it worthwhile.
Step 1: Designate a place in your home to store future sale stuff
Pick a closet or a room or a large box and use that space to store the items you intend to get rid of, if one of the items is your son who is playing too many video games, make sure you have packing tape to shut up the box. Throw some gallon size zip lock bags in there to hold smaller items. Those small items then can be sold together for a great price for the whole bag. Such a deal.
The point here is that when you finish a book you are not going to lend out - throw it in the box. Can't find the saucer for the cup? - put the cup in the box. Aren't going to wear that sweater again? - throw it in the box. Just bought a new iron? - put the old one in the box. Did you receive a gift you are never going to use? - in the box it goes. Do your really need 3 watering cans? - put at least one in the box.
This serves two purposes - it keeps clutter down and keeps you organized.