When standing on the board very still the red marker still moves around quite a bit and tells me I am unbalanced. Does this happen on everyones board?

Oh, yes, this does happen to me. The thing is that you only think that you are standing still. The Wii Board is very sensitive to movement. If you are breathing too heavily, for instance, it will pick it up. It will also pick up slight fidgets that one tends to filter out automatically.

The best way to keep the red marker still is to stand up straight - that is, back and neck straight and aligned - and to keep your eyes firmly on a point directly ahead on the wall. Keep your shoulders relaxed and your breathing light. Your body will follow your head, so as long as that is still, the marker will not move or, at the very least, it won't move very much. This is a very good exercise, by the way, that will help you to improve your balance.

Yes, even when you put on a lot of books on the board it will not stand still, because any vibration in the building will move it a little.