I did craft shows for years as my kids were growing up and spring shows are a lot of garden things as someone else mentioned. The little crouchet creations are so cute! The one thing I find so hard to take are a lot of things in the larger shows are "made in china" stuff and hard to compete. Also prices are very low.
The best thing to do... is to go to a few shows before you decide what you might love to do to get some ideas. My pet peeve has always been the copy cats... Who take an idea and copy it right down to the where the twinkle in an eye is placed! (Believe me, I have had few) I make scarecrows and larger welcome porch dolls and mine were always cuter and better made just because I had made them for years and perfected them but if you can figure out something that is your "own" and own it... you will have less problems with duplicates at a show.
Then look at the show and see if people are buying! It's great if there are a lot of people there, but if they aren't buying then it is a waste of your time and money. Talk to other artists and try to get a feel if they are happy with their sales. If you talk to a lot that feel like it is a dud of a show and they have cute things... don't do that show! It's not rocket science!
I do only one show called Sugar Plum in OC CA and moved 4 hours from it and still do it from time to time. It is the one show that has proven to advertise well and have a good following of loyal customers that wrap around the building prior to opening... and that is the kind of show you want! My daughter and I recently did their show after years of not doing it and we were there opening day and saw all the things going through. It was a Halloween show and definitely mainly Halloween things went through! Believe me, we took note for next time. We had very little Halloween and it was my fault for not doing my homework!
The trick is to communicate and don't do a show you know little about! Hope that helps!