Use easily removable tags for pricing. Do not use masking or duct tape. Price items on the low side. Not lug it back to the attic. Use a posting method that allows complete removal later.
Big arrows win.
Big arrows draw many into a sale, particularly if the address is hard to find. If you think an item is worth a huge amount of money, place an add in the penny papers or take it to a pawn shop, do not expect it to sell in your yard sale. Hang the clothes, don't leave them in a pig pile. Wash items, or at least wipe the mold off. Put your sale items in the front yard, not in the back, not in the alley, not in the basement.