Please put prices on things. I am twice as likely to buy if I can see price tags.
Price reasonably. You're not going to get above retail on loose DOTM or common CHUG figures. Nor above retail + tax for toys still easily found at retail. I fully expect to see $15 Beast Hunters Deluxes, and I completely expect to see them not sell all day.
Try to make deals, especially for multiple figures to one buyer. If you price as low as you can go, say that up front and don't be insulted if someone still tries to make a deal - just politely decline.
Try not to act grumpy or annoyed at buyers. I know it must be tough especially at the end if the day, but try.
Have a partner at your table. Necessary for toilet and food breaks and for help with transactions.
Take a bag full of plastic grocery bags - always appreciated by buyers.
Be prepared for a TON of looky-loos. But those same people may come back later to buy.
Please don't scalp MP03 Grimlock for $200. I know I'm going to see a ton of him there at that price and it's a pisser (and i'm not even looking for one, I've got my older TRU one).
As the day or weekend winds down, if you want it all gone then slash your prices.