The better things are set up the more money you'll get. If you have a way of hanging clothes on a rack and putting together outfits on display you can charge more.
Put like items together and items that can go together near each other (blender near a set of Margarita glasses, salad bowl near tongs etc)
Start early and stick to Friday and Saturday for the best prices. Sundays a lot of people don't come they think it's picked over.
If it's hot offer cold bottles of water/cans of pop.
Have a free box but make it one item per person or one item free when you spend $5.
Big ticket items out in front people like baby stuff, tools, fishing stuff, collectibles and sets of things.
Sometimes I even bundle items into a grouping (five pairs of pants the same size for example) thus getting rid of several items in one sale also this way if they want just one you can say you have to break up a set and get a couple more bucks.

Have lots of change depending on how you are charging. If you have stuff under $1 you'll need silver if not just some 1s and 5s.

Have someone out there with you to make conversation people feel more obligated to buy when you have personally acknowledged them and you'll have someone to help you watch for thieves.
Good luck let us know how it goes.

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