So easy, you're grandfather can do it!
It's a good idea to take a lesson your first time out, and you may want to continue taking lessons as your instructor can teach you a lot of cool stuff such as: jumps, spins, bumps, steeps, the half pipe, etc. Just about every resort offers lessons, but for those of you who are Do-It-Yourselfers here are the fundamentals of snowboarding.
You have got to stay relaxed. When you tense up bad things happen. An easy way to stay loose is to keep your knees slightly bent. This will also help you to absorb the bumps that are in the snow, kind of like shock absorbers.
Okay now that we are at ease lets try going somewhere. Start off by playing around with your board on one foot. (Your front foot) So if you ride regular that would be your left foot. And if you are goofy, you guessed it smarty; it's your right foot. Try skating across the hill for a while before you start down it.
Once you are comfortable doing that, strap your other foot in. Now we are ready to head down the hill. Remember to use your front foot to steer your board. (regular, left - goofy, right) To make a toe-side turn lift your heel up, press your toe down and move your knee over top of your foot. Your back foot will follow; you don't have to worry about it.
A toe-side turn is the same as walking forward. So that means that a heel-side turn will be follow the same movements you make when you walk backwards. You will lift your toe up, press your heel down and roll your hips backward. Look at that you are snowboarding.
Now that you are moving you may want to learn how to stop yourself. To do that all you have to do is turn more. If you turn yourself so that you are heading up the hill you aren't going to get far and will stop.
Remember these are only the basics, and the very basic of the basics at that. There is a lot more to snowboarding then what was covered in this section.