Set up from the front so you can see how it will look to your customers.
If you have plastic shelving units (those that can easily be put together and taken apart), use them to keep the more valuable / larger items off the table yet still on display. (Also helpful for storing anything you pick up along the way - might want to bring an empty box for your pick-ups.)
Be willing to negotiate prices. (And as others have said, clearly mark them.)
Be willing to trade, even with kids. This helped my table get lots of traffic and further sales because people were curious why so many people were gathered at my table and not at the others.
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).