If I was there, I'd come over to help! I love having and going to garage sales. Thought about writing a book on it....ha...ha...ha!
1. Make sure your signs are large, sturdy, and visible. Use large black printing on a bright backround and make the arrow BOLD and large. I hate it when people just list the address because most people are not a walking atlas (I don't know where Maple street is....). Make sure you have at least one direct route to your house from a main highway--and a sign at every corner with a large, clear arrow. I can't even count the amount of garage sales that I have not been able to find because of poor signing.
2. Have everything priced waaaay ahead of time. It is amazing what you have to do last minute and you don't want to be pricing the day of your sale. Price everything clearly. Any sort of sticker works fine and small signs work if you want a blanket price (i.e. Any shirt 50 cents, Any pair of shoes $1.00, etc...)
3. Set up as much as possible a day or two ahead of time...makes life much easier. And having a friend or two there when you open can be a lifesaver--especially if you need a potty break
4. Have twice as many bags as you think you will ever need, beg, borrow, whatever to get tons! If you are going to have your sale more than one day you may even want to have a bag sale your last day and having extra bags on hand for that will be great.
5. When pricing, keep in mind one important thing: how much am I willing to let someone pay me to haul off my stuff? If it is something that you are going to pack, haul, or donate after the sale, selling more at a lower price may save you a lot of work in the end. On the other hand, setting prices ridiculously low, may send a message that your stuff isn't worth buying. So, I'd visit a few sales in your area to see what prices people set and how much people are buying at what price. (I'll be honest, I'm lazy and don't want the work of setting up for two days, so I set low prices and have the sale one day. Usually there isn't that much left over to worry about at the end of the day) A lot of people set higher prices for the first day or two of the sale and the last day they go 50% off or have a bag sale, etc... Just depends on how much you want to sit in your yard.
6. Don't keep a large amount of cash in your box. Have a good stash of various bills in the house in case someone decides to break a $50 or $100. Have someone make cash runs to put it in a safe spot in the house when you get a lot in your box--wads of cash in your box is just too much of a temptation.
7. Be willing to negotiate. That one person that offers $5 for something you had marked at $8 may be the only person willing to buy that item that day. Make deals.
8. Pricing some item at so many for a dollar is a great incentive for people to buy more. For instance, at my last garage sale I had shirts for 25 cents each or 5 for a dollar and jeans 50 cents each or 3 for a dollar. Well, almost everyone who bought clothes walked away with either 5 shirts or 3 pairs of jeans and they were not in my way anymore! You may want to work out a different pricing scale for your area as clothes are hard usually to sell here. Our movies were $2.00 a pice or 3 for $5.00. Cleaned out!
9. Organize by department, just like a store. Womens clothes, Men's clothes, childrens by size, toys, kitchen, tools, gardening, etc... Clothes by size is wonderful as well if you have a variety. Some people will look if you have a sign that lists their size. Fold or hang clothes, arrange everything as neatly as possible and plan to make frequent walk throughs to straiten as the day goes by. As a pp said, nice stuff that is disorganized doesn't sell well. See if any neighbors will let you borrow extra tables and tarps.
Ooooh! I better stop before my post gets any longer, sorry. Good luck on your sale!