I agree with film8ker. A shooting script is a vital tool in the production process.
My personal preference as a director, is to use three different documents to understand the shoot. A shooting script, which tells me which shots I've planned for each scene and allows me to mark them off once they are in the can. This very usefulk, because the shots are placed next to the dialogue and action on the page, therefore I can quickly reference the coverage on the scene.
The other tools I use is a floor plan, on which I block out the movement of the actors and then mark in my camera positions. This is incredibly useful, because it shows the all the angles and gives me a clear indiction of whether I've got sufficent coverage. It's also a good way of being completely sure that I haven't crossed the line. Also, because I always carry spare plan sheets for each location, if I'm running behind schedule or I hit a technical problem (such as a last minute change of location) that I can't fix, I can rework my shooting plan in a matter of seconds.
The final tool is the storyboard and primarily I use that as a way of communicating clearly with the DOP what I'm looking for on each set up. It's much faster and clearer to show the DOP with a storyboard what you want, than explaining.
I know that it's possible to do the job using just one of these tools, but having all three in one file means I've got a complete understanding of the shoot and flexibility to deal with the unexpected.
Oh, one of the things I've started doing on location scouting trips, is taking digital stills from my camera positions, framed roughly how I think I'll shoot. I then transfer the stills onto my storyboard sheet at a low resolution and semi tranparent (about 68%). Then I print them off and draw in the characters over the location photos. Because of my professional still photography background, I've found this a great way to produce storyboards.