G'day Alex,
When I'm teaching a student to line up the runway, I advise them to stand parallel to the runway, & don't move, set up the approach pattern, & bring the plane around onto final, so that with your head turned to the right, or left, depending on direction of approach, the plane looks like it is heading straight at you, & in the middle of your view.
Fly a low pass, & notice that the plane is still about 4 or 5 metres in front of you, as it passes you, because you should not be able to see squarely over your shoulder, you will be looking slightly ahead of your shoulder, try it while reading this.
Be aware your shoulders should be parallel to the runway, for this technique to work.