Make good use of your vertical space.
Accept credit cards if you can, and put a sign up saying that you accept them. (PayPal, Square, etc. are good for craft fairs.) As far as personal checks, I put on my sign that I don't accept them, but truth be known, I will accept a check from (say) a member of that organization ... like if the event is at a church, and the check-writer is a known church member. The sign mostly backs me up should someone want to write a check that's giving off "hinky vibes", if you know what I mean.
Take more change than you think you'll need. For some reason, people love to whip out a $50 or $100 bill for a $5 purchase 15 minutes into a show.
Offer quantity discounts if you can. $5 each or 3 for $10. Many people go for the better deal.
Have your business cards handy. I also like to print out my craft fair schedule and hand it out so people can find me. Both have a link to my Facebook page and website. (I do a lot of craft fairs.)
Ditto on trying to sell stuff that nobody else is selling. That's kind of hard to do these days, but even if there are other people selling the same thing, many potential customers do notice whose items are better-made. So make your stuff extra-nice, and display it well.
Don't underprice yourself. I was bad about that when I first started doing craft fairs, thinking it would be smart to give people as good a deal as I could, but it backfired. It's a psychological thing, I guess. A $2 item is perceived as being much better-made than an absolutely identical item priced at $.50. Weird, but true! So be fair to yourself when you price your stuff.
Buddy-up with your neighboring vendors. If you're by yourself, one of them can watch your booth for a minute while you take a potty break (and vice versa).
Don't pack up and leave early. A lot of times, last-minute shoppers come through, plus it kind of looks bad to skip out early. (barring an emergency, of course)
Have a basket of candy to give out. It's a nice little gesture, plus it keeps a potential customer in your booth for a few extra seconds ... more time for them to spot something they can't live without!
ha ha
Be sure to personally thank the event coordinator afterwards, and ask if you could be notified of future events.
But most of all: have fun!
