Weights are the most important thing....next to the tent...get an ez up or another brand like it. I have 4" PVC pipe with a bottom cap and filled with cement..another cap at the top, with an eye bolt inserted in the cap. I have 1 for each leg, but for windy conditions I have another set to add on. These weight about 28# each.
Cinder blocks tied with nylon rope will work, so will weights from a weight bench...
Use a table cover that goes to the ground, so you can store boxes,etc. under the table....don't use plastic table covers, it makes it look amatuer.
Be prepared for all weather. I also have clear shower curtains to attach across the front of the booth so people can come in and shop, but my merchandise doesn't get wet. You will need 3 shower curtains and 2 5' pieces of PVC plus a connection in the middle.
Good luck

I have a large check list!!
something to cover your items quickly in the event of a sudden rain shower and to cover the sides of the rent at night-most of these events will have security but check!
snacks,water,sunscreen, baby wipes and hand sanitizer, business cards(you will have tons of other craft shows looking for vendors for their show)
take something to work on!! it draws attention and they will come look! I have been invited so several shows this fall because I demonstrate my craft!
Be aware- this isnt a quilt show they will want to touch!!
some shows I do better with small items some with large

as someone else said don't get discouraged!

Thank you for all these useful tips! The weights in the PVC pipe are a great idea. I was thinking of using weights at the bottom of the four tent poles, wouldn't have occured to me to hang them off the tent! And the shower curtains are a good idea, too. This forum is just so great, I was just saying to a friend the other day that there isn't a question in the world that you don't get answered in this forum!

Set your booth in a U-shape or L-shape with your tables, quilt racks, etc. Gets people to walk IN to your booth and they take more time to look at things. If you just have your table across the front, they only scan as they walk by and they don't really SEE your inventory. If tax is included in your price, have a sign saying so. If you are going to take special orders, be prepared with prices listed in writing.