See if you can search Martha Stewart for garage sale info. Years ago she had a great article on setting up a sale.
Make it like a party, have some fun music playing.
If you are selling anything that uses electricity, including lamps have a extension cord ready at that table so people can see stuff working.
Make sure anything glass is clean, You would be surprised what people will buy if it looks cared for.
Keep like things together.
Make pricing easy for you. I found it best to wear a carpenters apron w/ pockets so you don't have to keep going to one spot and not be able to keep your eye on the money.
If it is going to be a nice day, have some coolers with canned drinks and even if you priced it just to pay for it, people appreciate your thoughtfulness.
Have good signs posted the week before.
It is a lot of work, just remember your goal, to get rid of "stuff". Everything that goes is a good thing!
peace