I usually use painter's tape of the width I am wanting. I lay a long piece from corner to corner of the item and stitch right along the edge on both sides (not stitching the tape hopefully). Then I move the tape so that it is right along side one of the stitched lines and sew down the other side of the tape. Just keep moving the tape (or replace with a new piece if needed) until you get to the corners. Then turn around and go corner to corner in the opposite direction. This method does not require any marking on the quilt which is why I like it. When there is appliqué along the way, I just stitch up to it and along the ditch edge of the appliqué to the next line and go back to the edge. I do the same at the edge of the quilt so that I don't have to start and start so often.