I had a garage sale a couple of weeks ago, very successful...
First I put an add in the paper,then put signs and arrows up all over town two days before.
I priced everything with pre-printed stickers from Staples. Everything was in dollar amounts, and then I had two boxes of stuff that were marked 25 cents or 50 cents on the box. People expect to see prices, they do not want to haggle. Unless they are looking for specific items and are antiques collectors, they just want to know how much you want for something.
I also had a lemonade and iced tea stand with cookies my daughter helped me make for sale, I honestly made about $50.00 just on drink sales since it was a hot day and people love fresh squeezed lemonade and homemade tea.
All clothes should be hung up and easily viewed, and toys, puzzles, etc. should be on a table for display or on tableclothes on the ground.
If you have a book shelf you can move easily, this is the best way to sell books, price them by shelf, 25 cents books top shelf, etc.
About an hour before you are ready to clean up, drive around and mark your signs 50% off everything...
Once your sale is over, remove any items you do not want to trash or give away, then put a curbside alert on freecycle explaining some of the items up for grabs. People will flock and take whatever they want at this point and you will be left with nothing to bring back into the house.
You can also put a free ad on craigslist in the garage sale section.
Good Luck!