With my local flee market you have the more permanent businesses and the food area. They try to look like everyone else, but when you're selling tons of used games, used books, cell phone cases, used DVDs, etc. it's obvious that it's your business.

Then there's the open air stalls where regular people come to sell stuff that was clogging their attic.

You have to get there really early to find good things at the open air tables, but you can find good deals at those tables.