|I don't know how useful this tip'll be, but when my son was doing some sewing this past month, it was a big "AHA" moment for him when I told him about it. Hopefully it'll help someone else.
If you look at your presser foot, there is a marking on the center front that shows where the needle will sew. Match this marking with the line you want to sew on.
If you're appliqueing something, this is where the center of your stitches will be. Match this point to just inside the edge of the fabric patch.
Just don't watch the needle to sew straight. Use the guide lines on the throatplate or the presser foot.
Hope that helps!