I have skied (downhill) since I was 9 or 10 years old, so by now I consider myself a pretty good skier. But none of it helped when I first tried a snowboard. Both feet tied to the board I couldn't stay up for a moment. Now, after taking a couple of lessons and using a snowboard for maybe five or six times I'm finally getting better. I can often exit a ski lift without falling, and do several runs without hitting the snow with any body parts. One trick is just getting a bit more speed and letting go, boldly leaning in turns. With a little bit of confidence it goes much easier.
Compared to skiing, snowboarding is definitely more fun. I feel that there's more variety when you can go facing uphill or downhill, left or right foot in the front. I really should do it more often than my current average of once a year.