As usual, Roger is spot on the mark. He has a way of putting things in words that I can never manage.
Take a look at the footstrap articles by Guy Cribb, might give you some things to think about.
Not all agree with some of his ideas (including myself, he has very fixed ideas with no room for individuality especially when it comes to the harness and lines) but he does give some very good advice and there is no doubt that he is an extremely good teacher and windsurfer. Everyone has different opinions and that is a good thing IMO.
Another great learning resource is the Peter Hart DVDs. His commentary is superb and funny while instructional. One of the best.