I have found that when it comes to quilting straight lines I do best when using a piece of computer paper. Usually when doing straight lines you go from corner to corner diagonally across the quilt or you parallel a line. Doing straight lines I generally use my walking foot. I lay the piece of paper from Point A to Point B and sew along the edge of the paper. Then I move the paper to Point B and C. Across the quilt. If I am doing lines parellel to that the first line of stitching I cut the paper strip the width that I want (1 inch, 1-1/2 inches, etc). You can pin the paper if you feel it slipping on you. Also if you have lots of seams to sew through it might be helpful to pin in several places.