As you decrease your aperature, you increase your depth of field. As your depth of field increases, you are able to focus your lens closer to the camera and still have infinity be in focus. Make sense? In other words, it's a way to insure that everything in your scene, from foreground to background is in focus. You do this buy stopping your lens down and then focusing the lens closer to the camera rather than at infinity. I think this is easier with DSLR's as they naturally have more depth of field anyway.

Some lenses still have a hyperfocal scale on them. They give you an idea of how close to your camera you can focus your lens and still have your infinity be in focus, for each f-stop. If your lens doesn't have a hyperfocal scale, most photogs will focus about one-thrid of the way into the scene and use their depth-of-field preview button to make sure infinity is still in focus.

Oh, and yes bracketing is another great idea. Set your camera to auto-bracket and let it fire fire 3 shots with every shutter push to save you time.

Rick