One of the biggest suggestions that I was given before I tried a flea market was to not sell what everyone else is selling. Do have the items that others are selling, but also have a niche of your own. On top of having your own niche, research it and have as much knowledge as you can for the customers.
My niche at the flea market I set up at late last year was cb radio equipment and sports cards, and those are what made my most profit. I have been in the cb radio business for 6 years and have been into sports card collecting/trading/selling since the early 90's.
Another great suggestion I was given was to do hands on research of the flea market you are going to set up at. Make a few trips to the flea market a few times before you set up. See what all is available for sale and what a lot of people are actually buying, what times of day the most traffic is there, and what areas have the most traffic. Also, take notes. Not only while you are researching, but while you are selling. If you can't go to the flea market yourself, have a friend or family member go check it out for you.
Remember it is kind of hit and miss on what sales and when it sales. The more you know the better you will do.
