Anne,
A great thing to use for quilting designs are cookie cutters. I have a huge collection. They usually come in simple but recognizable shapes. If you are quilting on a busy or dark background and marking is hard to see cut designs out of interfacing, spray the back of it with adhesive spray and stick it on the quilt where you need it. After quilting around it peel it off and move it to the next area. It sure beats premarking the whole top. You are going to mark it before you baste it together, I hope.