Historically, I have done very well at cons. We've increased our sales every con we've ever been to, and every year our revenue exceeds that of the previous year, mostly from cons.

That being said, most people hate cons. I thrive on them. I love meeting the fans, selling the fans, and making deals. Of course I'm a salesman by trade (and a right good one at that) and a business owner by blood, so it comes a little easier to me than it does to other people.
But anybody can sell, they just need the tricks. I'm not going to overload you right now, but here are a couple of tricks you can employ RIGHT NOW to make you sell better at whatever convention you attend next.
BEWARE, some of this flies in the face of what you've been told your whole life.

1 - ENTHUSIASM. WHERE IS YOURS? I know you're passionate about your product, otherwise you wouldn't have driven for hours, paid a booth cost, and outlaid so much money in order to get to a con. So why aren't you showing that enthusiasm to your customers? At least 60% of booths look like they would rather me die than buy. They don't smile. They don't engage. They just let the product speak for itself. Boo on that.

2 - PEOPLE WANT TO BUY FROM VENDORS THEY LIKE. At the end of the day, I can buy a button, sticker, or cool plush toy from any number of vendors. There are a half dozen that sell what you brought, so why would I buy from you? Because I like you. I can't tell you how many sales I've made just because I made a connection.

3 - BUNDLE. This is what flies in the face of what you've been told about not lowering prices or giving deals until the last day. Screw that. You know your profit margins and you have a willing, interested client in front of you. If somebody is tipping over the edge, make it worth their while by throwing in something with their purchase. I usually throw in a copy of my book Paradise as an incentive. If it kicks somebody over the edge, I made more than enough to justify the loss in profit. Everybody wants to know they got a good deal.

4 - DON'T LET THEM LEAVE. Here's the key. If somebody leaves your booth, they aren't going to come back. They will find something else they like and buy that. There is very little chance they will swim back upstream just to see you. You have to do whatever it takes, within reason, to make them buy from you and at LEAST leave an impression. Make they join a mailing list or something.

5 - ENGAGE WITH PEOPLE WALKING BY. The people walking through your area are perfect consumers. They want what you are selling. Why are you letting them pass without saying hello? Engage them, ask questions, seem interested in their lives.
These are just a couple tips from me to you. By using them you will increase sales because you'll have more quality foot traffic asking about your product.

Hope it helps. Make sure to check out freekickstartercourse.com too in order to start your journey on the right foot.