something that has helped me determine where the needle is coming dowm in relation to the edge of the presser foot. :
I use an index card that has lines printed at 1/4 inch intervals or 1/4 inch grid graph paper -
Line up the edge of the foot on one of the lines, then sew to see if i need to move the needle.
This is, of course, assuming that I line up my fabric with the edge of the presser foot.