If you really want to previsualize your project before shooting, either for your own benefit or to pitch a project to financiers, your boss, or your mom, consider doing a "living storyboard"- that means:

• draw storyboard frames
• use the "Photo" button on your camcorder to capture each storyboard frame to DV tape
• capture the "footage"
• edit the stills together in your editing software
• do a scratch audio track in which you do all the voices (and music and sound effects- and even comment on certain shots).

This secret has worked well for others- for example, Elyse Couvillion used this secret to present her idea for "Sweet" to Allen Daviau, who agreed to DP her short based on her living storyboard created in Final Cut Pro.

Check out Sweet on DVD here (includes commentary on the short).