My third tip: remember that you're trying to sell. The customer is NOT always right, but should always be treated with respect and courtesy. Most customers are going to ask you to negotiate your price. Don't be offended by this - if you feel you really can't come down on the price, say so. But don't feel like it's a personal insult. If you can come down some, then you may gain a recurring customer.
Many browsers will want to talk. They may want to tell you about some game they attended thirty years ago. They may want to ask about the value of cards they have, which will most likely be at home and not at the show. They may or may not actually buy anything. Unless you're extremely successful, more attendees will NOT buy than will buy. Be patient with them. Even though I'm not usually the most outgoing person in the world, I find this one of the enjoyable parts of the show - being able to talk to a wide variety of folks. Be patient with the kids. They may have little cash in hand, but they are your future customers. Always try to keep a smile, be friendly, and ask if you can help them find anything. If they like you it stands to reason that they will be more likely to buy, and, more importantly, come back to the next show.
I have a few more suggestions. What should you try to sell? I say anything you have. You may be surprised at what people are looking for. Ask the show's coordinator about any special rules such as restrictions on signs, whether you can have stackable display cases, or even what you're allowed to display (books, clothing, trinkets, even non-sports items such as coins if you're interested). Know what size table or area you're getting so you can estimate how much stuff you can display.
Shows may vary in size from those (like ours) that are maybe thirty tables and run one day a month to those like the National which has hundreds of tables (over 600 dealers expected this year) and lasts four+ days. Of course, the cost to you varies accordingly. Check the Beckett web site show calendar for shows in your area.
To sum up my most tips for setting up a card show: one, and most important, be as organized and "user-friendly" in your display as you can be. Two, be as prepared as you can be with your prices. Three, try to present a pleasant, friendly personality to your customers. And, finally, be sure to have fun. Good luck with your show!