If I wanted to have a successful yard sale, where should I advertise other than 4042 classifieds and signs at nearby main roads?
Your best bet is to get big poster board with large markers so that the writing can be seen for some distance. Make sure that the morning dew will not wilt the signs or the letters will run - get posts for both ends of the board. Place those signs on main roads then make sure that all signs leading to your sale are the same color. Also make sure you do not space them too far apart or people will assume the signs are old or you overslept/cancelled the sale.
I had one a few months ago that was successful. I did 40/42, CraigsList, Cary yard sales.com, and put signs on the road.