Hi Patty, welcome to the board.
Quilt show judging can be very Subjective that is why there is no difinitive guide as to what judges will be looking for. A quilt may ribbon in one show and not even place an honerable mention in another. There are certain rules of thumb that could be counted against the quilt such as no cut off points, that binding should be filled and of uniform width and lay flat, that seams should run straight and intersect at the proper points, but really for the most part it is what the judge likes and appeals to him or her if the construction is done well. Some judges are sticklers for ditch quilting, others not so much.
I do not show on a national level only local. I enter a show for the fun of seeing my quilt hanging amongst all the others and never enter with any expectation of winning anything. If I do happen to place, I am delighted but if I don't, I am not disappointed as I had no expectations to begin with. I think just entering for the sheer fun of it is the best way to go about it.