Do you wax your skis regularly? Keeping your bases nice and hydrated is probably the best thing you can do to keep your skis in good shape. A dry base is more brittle and will scratch easier. (Unless you have an extruded base, then it doesn't matter as much b/c the base won't really take wax anyway.)
Also, if you ride a lot of rails, its a good idea to detune the edges underfoot before you use them. A rounder edge will be more resistant to cracking than a factory sharp edge, b/c the impact is distributed across more edge surface.
This may seem obvious, but don't clack your skis together on the lift. If you have a straight sidewall ski, this can actually really chip them up. (I'm not saying you are doing this, I doubt its a real problem, but I have seen people do this to their skis and then complain that the topsheets are mangled.)