Put a nice table cloth down. Medium to dark red or green really sets off the colors of the trains.
Bring a counterfeit bill pen, available at any Staples or similar office supply.
I am sure that 98% of everyone at the show will be honest, but there are large numbers of counterfeit $20 bills out there in circulation, that many people unknowingly have in their wallets. As well as $50s and $100s. (At one retail place I frequent, they use a counterfeit pen on anything $20 or larger, and for good reason.)
When you are counting the stack of money handed to you, don't engage in any chit-chat. Very very easy to accidentally lose count and end up with a lesser or greater amount than the price.
Also, bring a small bright flashlight and a medium size magnifying glass. Often, the lighting in a convention center is really really bad, and a flashlight or glass can really help you make a sale.
Put all of your show supplies (pen, paper, counterfeit pen, flashlight, etc.) in a cardboard school pencil-box, available any Walmart etc. That way, all of your stuff is one box and not falling out of your pockets. Bring at least 4 ballpoint pens, because they have a tendency to grow legs and walk away during the day.
As others have mentioned, bring lots of change, in $1s and $5s and $10s.
As far as pricing, you have to decide whether you are trying to make a profit, or trying to get "all of your money back" or trying to make a sale at what you absolutely know to be a fair and reasonable price.
When I go to shows (for my other hobby), I am there to SELL, not fool around. I know exactly what the item is worth, and price it about 3 to 5% below that price. I rarely negotiate, and they sell fast. When someone tries to negotiate hard, I just tell them (very pleasantly), "Hey, I'm sure that you have been in this hobby longer than I have, so I am sure you know that I have priced this below fair value. Why?, because I am here to sell it. Bargains don't last long at shows, so if you really don't want it, I am sure that someone else will take it." Smile a lot.
Mannyrock
