People do not like to look at stuff on the ground. Things on the ground do not look important. Older people cannot bend over to look at things.
Try to borrow or rent tables. It will increase your sales.
Of course I am talking about clothing, kitchen stuff and household items.
Gather alike things together so that it makes sense.
Clothing, Books, kitchen, Bath, Bedroom, Collectibles..
Be willing to make deals to get rid of stuff. Otherwise you will be stuck with the stuff either donating, trashing it or packing it..
The goal is to not have to throw it away and to get at least something so people will take it away for you.
Try to have help. One person is not enough to collect money, answer questions and keep things tidy.