The thing to remember is not to bend over at the waist (which I've seen happen when someone is trying to reach and sweep the pleats) -- it'll raise the back hem even more than just the act of sitting will already do. This includes when you're sitting down or picking something up off the ground. Lower yourself with your legs (just remember in the case of picking something up to watch it from other angles, too).

Letting the chair sweep the pleats for you when you slide back is a good idea.

I have to admit, I hate cloth seats in low cars when I'm wearing a skirt of any kind (even ankle-length). First, I have to squeeze in because of my height, and then once I'm in, I lift myself slightly and adjust my skirt so it's not bunched up due to the grabbiness of the fabrics.