I knew a lot about selling in person from my upbringing in the carnival and doing fleamarkets.
Here's a good link for a lot of those tips
But I learned a few other goodies as well.
A good tent is a must!
Don't bring paper stuff when it might rain.
If it does rain before noon, all hope is not lost, but if it keeps raining until lunch, then you may have a problem on your hands (this is from my neighbor, who makes his entire living off of craft shows).