Honest ..this works.
Get a bowl of cool water, add a small handfull of flour (any flour will do, plain, SR, or cornflour) just enough to give a watery semi skimmed milk consistancy. Wash your window with it. Dry it off straight away with kitchen towel. Then get a dry cloth (micro fibre cloths are best) and polish. It hardly takes any elbow grease so don't worry.
Beautiful windows, no smears! It also clears away any other chemical residues that your windows have collected over the years.