Not easy to do with a consumer camcorder but here's a few tips
You'll need a few manual controls on the camera
Step 1. Get in as close as you can to the main point of interest (and focus) in the frame leaving the maximum distance between your point of interest and the background
Step 2. Change setting to manual focus and focus on main point of interest in the shot
Step 3. Leave your cameras auto exposure on and put ND filter to maximum, if enough light to shoot with, set cameras exposure to manual, if not enough light, change ND filter to next lowest and exposure and try again till you have enough light to shoot with.
You're now ready to shoot
And here's a little video using these tips http://www.digitalgloss.com/ShallowFocus.wmv