If you're not sure how to initiate a conversation at a show with someone standing looking at the show hamsters who's a club member, a good opener is "do you have any hamsters in the show?". Then a whole world of how are they getting on, how many have you got entered etc. opens up
Another good way of meeting people if you go to the show for the whole day is to volunteer! I've got to know so many people through helping in the kitchen or on the tombola not just through stewarding.
Exhibitors don't bite, though I may want to growl sometimes if I'm in the middle of writing all the duplicate prize cards and someone wants a long chat
If someone says now's not a good time, it's not personal and do go back later.