You don't need to be a great artist to storyboard your script (in fact, the DP for "Raging Bull" said in the Special Features that it was better that Martin Scorsese's sketches were poor). I made a storyboard template that you can download for free in the Attachments section at the bottom of this page. Print off a bunch of these pages and start sketching.

(NB: I have also made a 16:9 version available. However, Aspect Ratios is another subject all together, and if you don't know what you will be shooting in, I would suggest you stick with 4:3, unless you know you want your movie to look like a "real" film.)

The purpose of storyboarding is to get an idea of what shots you want in your film. It will also help you to begin to see what the movie is going to look like in the final product.

Armed with your storyboards, you will be able to figure out where you want to place the camera on your sets, and so will be able to develop a "shot list". This list will help speed up production by letting you know what shots will all be taken from the same camerea set-up. This will save you a lot of time on set, and spare you the hassel of moving the camera back and forth every couple of shots.

If you storyboard every shot, you will be able to do Pre-Visualization with more accuracy.