Use a long stitch length, loosen the pressure on the foot, if you have that setting. I have drawn lines with a ruler 1/4' from the seam and sewed on the line. This keeps the bulk of the seam out of the stitching and my stitch line is straight. For fast machine quilting, I draw a diagonal lines from corner to corner and middle and just sew on the line all the way across starting in the middle. I can fill in or just draw more lines in each section.