A couple of extra pointers:
[list=1][*]Be at the right speed. Some people have a tendency to add a few knots extra "for luck" in a crosswind. A PA28 will float if the speed is too high, and it's not easy to keep floating over the centre line as your speed decreases.[*]Treat your PA28 as though you were landing a taildragger - don't relax until the end of the landing roll. After landing, focus on a point at the end of the runway, and use the rudder to make sure you don't let yourself deviate left or right. (Most people seem to end up on the left side of the runway.... )[/list=1]
Something that really helped me when I was learning was a long session of circuits with an instructor at an airfield with a very narrow runway. Wide runways had let me get away with poor technique.