Pick products that have high demand, high profit margins and little competition.
Look at the age, sex, income levels and other identifying characteristics of the people at the market.
Take care in displaying your wares. If your booth looks like the floor of someone’s messy closet, buyers won’t trust that you’re selling quality products. Check online for Craigslist for inexpensive retail display racks to give you more space and a more professional look.
Assess your weekly sales by product and profit margins. Wait for consistent sales of a particular product before committing to bulk buys, especially if the same people come to the flea market each week.
You want your patrons to like you. Be friendly; engage customers in conversations on subjects that have nothing to do with your merchandise.
Don’t try and be greedy. It is much better to sell 500 items at a $1 profit than 100 items at a $2 profit.