Get in shape. Don't try to ski yourself into shape. You'll enjoy skiing more if you're physically fit. Set a goal. Set a target for yourself to work toward all winter long. Ski up. Ski with people better than you, it will help you improve. Take a lesson. The best way to become a better skier is to take a lesson from a qualified instructor. This will help you avoid getting used to bad habits. Try new things. Challenge yourself to improve your skiing ability. It's the only way you'll get better. Using your poles. Plant your pole out in front of you where you're about to turn. Visualize your run. Visualize your run before you start. It will help keep you focused and confident. Warm up run. Take a warm up run to get your ski legs before you tackle difficult terrain. Watch videos. There are tons of great videos of pros skiing. Watch their form and learn.
The "Get in shape" tip is especially important. I learned that the hard way. I've strength trained quite a bit in recent months, so I think I'd be a little better off this time around. Lower body strength is so very important in skiing.