What I do when I am showing someone a quilt in progress, I ask them to please tell me if they see anything wrong. Another thing I do during the process is periodically take a picture and then blow it up on my computer. I have found many things that I otherwise would not have seen. If the quilt is finished and there is something wrong, then I just consider it my "artistic license" and don't worry about it. Chances are most people will never notice.