First of all, there's no science to this. I did a show this weekend that was fabulous for me! Probably at least a few folks didn't do so good....first point.
How do I decide which ones to go to?
First of all, ask other artists, crafters, weavers....folks who do what you do. I ask other creators of fine craft, jewelry and glass....there's not much point in my asking weavers about shows...they travel in a different circle. Have they done the show at least 2 years in a row? Were crowds good? Were sales good? How did they treat the artist? A good recommendation from someone that's like me goes a long way...
If I'm contemplating a show, it doesn't hurt to ask folks who visit your booth..or your colleagues and friends, if they've heard of the show. If they haven't, it could mean that it's not established OR it's not being promoted well. A "must" for getting attendees/buyers to the show!
I also look for established shows that are well-promoted and which are promoted for the kind of work that I do. Case in point: The Country Craft Peddler shows have been going for at least a decade, do decent promotion, etc..but not at all to my audience. I'm just not interested in doing those.
Finally, I want to understand/ask these questions, particularly of a new show:
1) Is the show juried? If not, how do you monitor/guarantee quality of the artists and crafters exhibiting?
2) Do you allow resellers to display/show/sell? Does the show require the artist/crafter to be present at the entire event?
3) How will you promote your show? Who is your audience for this show? Ask for specifics, including the timeline for promotion. The bigger and longer lead time, the better. Ask if they support artist promotion: do they supply you with postcards, signs, e-mail/facebook/twitter markers, etc.
Finally, and I've written about this before, I have a rule that I do a show at least three years in a row before deciding it's a dog or a fabulous show.....I believe that if it's a truly good show, your first year will net some sales, but folks won't go expecting YOU to be there. The second year, folks who aren't on your mailing list may go hoping you'll be there...remembering you from last year. The third year, they'll expect you to be there... and will purchase accordingly!
So, get out there...apply for some shows, and share candid feedback with fellow artists and crafters so that the quality of shows get better! It helps us all!