Keep in mind that if you're entering a machine quilting show the quilting really needs to be pretty spectacular. Here is a link from one of the shows so you can see what the competition is like. If you do a search you'll find links to the other shows and most of them will have rules for submissions.
http://www.mqsshow.org/
I would say, be very original and creative and make sure your work is the very best you can do.
I'd get my feet wet, so to speak, with some smaller shows where you'll get feedback from the judges. That really helps you find any areas that you're lacking in.