I think people have already mentioned most of these things but anyway...from a yard sale lover...(I have never had a yard sale myself, but I know what I like!)

I also hate it when everything is scattered on the lawn, I'll just leave or might look at a few things, and then I'm outta there. I don't have the patience and I have a bad back so I don't like that..

Put prices on everything! I hate hate hate when, there are no prices on anything. I don't like to haggle or guess prices...if there are no price tags at all I will leave and find another sale.

Keep expensive/small stuff right in front of you, or have one of your helpers 'guard' it. Almost everyone I know who's had a yard sale, also has a story about small/electronic/expensive items being stolen by kids, by adults, by their own next door neighbor..Someone on this board years ago posted about a bunch of people pulling up in a church van and stealing several of her things.

And be careful with the money box! Once at our next door neighbors I grabbed a fishing tackle box I wanted to buy for DH, I carried it around for like 5 minutes and then set it down and opened it up to look at it..it was full of money! Man was my face red..I kinda gasped and gave it to the neighbor right away and explained...I was kinda embarassed lOL But they hadn't even noticed it was gone. Yikes.