i'm not a judge, but have been judged a few times...some of the things...
binding is big...is it 'full' evenly and to the edge? did you stitch the miter closed (lots of people dont know you should) is it even front and back with even crisp miters? is the quilting even/balanced throughout the quilt?and appropriate to the quilt design to enhace, not detract? now construction...are your seams straight, stitches even, any applique or embellishments secure?is it clean, free of odors and pet hair? is it square?
these are just some of the things they take into consideration; have to add color/design/wow factor...even quilts that take your breath away can miss the mark with judges....sometimes i think it comes down to...too many quilts not enough prizes :( although that shouldn't be...never take it personal and if you have a quilt judged in a show the judge writes up a 'summary' read it, take the recommendations and criticizm as a learning experience and try again. i had a quilt that took a 1st place and viewers choice award in one venue and did not even merit an honorable mention in another...you just never know