Welcome to Epic. First off, when you do cross your skis, uncross them by picking up the ski on top and stepping it to the side. In order to step like that you'll need to get your weight centered (this comes naturally when stepping) and you'll end up putting your skis in a position that's easier to keep uncrossed.
What level skier are you and how much experience do you have? Are you skiing with your skis parallel or partly in a wedge?