Its really just a matter of how much give the skirt material has as you walk. The larger the stride and the tighter the skirt the more it is forced to ride up. In addition the material will tend to cling to the skin, that is why tights or stockings help.
This probably also explains why HL dresses don't seem to suffer so much because of the elastic material in them; certainly I've never had a problem with the 3 HL dresses I have.
So smaller steps - higher heels help in this respect, perhaps a slightly less tight cut skirt and stockings are my solution.