1. Enter you quilt into the correct category, read the show rules and be respectful of the parameters.
2. Your quilt should be clean and show-ready. No pet hair, stains, or odors.
3. Visual impact is the first impression, a visually striking quilt stands out from the others.
4. Piecing technique is very important. Points should be sharp, corners should match, etc.
5. Applique technique is judged equally to piecing, curves should be smooth and pointed leaf tips should be sharp and not blunted.
6. Workmanship should be neat and tidy.
7. All threads tails should be buried and shadow-through from darker seam allowances should be trimmed before the quilt is layered for quilting, judges really dislike shadow-through!
8. Long, straight seams should be straight.
9. Quilting should be evenly distributed across the body of the quilt.
10. Finishing is your last area to impress. Be sure that your mitered corners are sharp and square and that the batting fills the binding all the way out to the edges. Long straight edges should be just that, no waves or ripples!
Those are (what I can remember) to be the finer points that can make a difference in placing your quilt into ribbon consideration. Of those listed above I probably heard numbers 8 and 10 dictated to judging sheets the most often.
Personally, the most important bit of advice that I can offer is to make quilts that you love and enjoy every step of the process; do your best work and the rest will take care of itself.
Life is Good!