My girlfriend and I are garage sale junkies. We've had a few over the years. Here's a few tips I can share with you.
Make sure your items are generally clean.
Toys sell.
Stuffed animals do not sell.
Glassware like mugs and vases will sell, but for only a quarter.
Spread items out on tables or tarps on the ground, we don't like to dig through boxes.
Adult clothing usually doesn't sell, except for jackets or hoodies. If you itemize on your taxes, you're better off donating it to Good Will.
Children's clothing, separate by sizes.
If it's broken, throw it out.
Have boxes or bags available.
Make sure you have change.
What determines the price? Good question, it's basically what other people in your area are charging for similar items, and the condition of the items. Also, how bad do you want to get rid of it.
Personally when I go to a garage sale, I want to see the items priced. Of course, there's usually haggling involved. Let's say you have a bike you want $10 for, price it at $12 or $15, you may get the full price, but you'll have room to bargin so you'll get your $10.
If you have a box full of a similar items (like craft supplies), priced at $.50 each and you notice someone digging through the box, you know there are 12 items in the box so potentially you could make $6, offer them the whole box for $3.00.
Make sure you advertise your sale. Take out an ad in your local paper. In addition hang up signs, remember as your driving by it's difficult to read the signs, so don't put a lot of info on it. If your house is in a subdivision and requires several turns, draw arrows on the signs. And please take down your signs.
One person's trash is another person's treasure. You may think it's junk, but someone else may want it. So put it out, if no one buys it, you can just toss it after the sale.
Good luck.