If you make lots of different things, group similar items together.
Try and get some height on your table, it is a more efficient use of space, it only needs to be a set of book shelves.
Use clamps to attach your table cloth to the table - there’s nothing worse than someone accidentally pulling everything off your table!
Go for a range of prices with your items, having items under £5 and under £10 tends to provide more impulse purchases ( as long as it works for your costings!).
I tend to give offers on items related to upcoming events/holidays but make sure you don’t discount so much that your profit is negligible!
Try to make eye contact and say hello to everyone who visits your table. I tend to only start talking more when customers begin to show an interest, highlighting any offers or informing what something is made from ( like the fact that I use sterling silver earwires).
Make friends with the stallholders around you, it can help with passing time if things are going slowly, customers seem to like having sellers that are happy, and when you need to nip to the loo then they can keep an eye out and inform a potential customer that you’ll be back shortly. If they have done the event before then they can also be a really useful resource for info about previous footfalls etc
Good luck and don’t panic!