you will need a DSLR, a tripod, a cable release, a wide angle lens (I used a fisheye last year but was pretty close to the action), and a lawn chair to kick back in.
Set the camera/tripod up so the fireworks will explode in the field of view. Set the ISO low (~100-200 or so) to reduce the noise. I set my aperture to about 5.6-8 or so. I put the shutter on "bulb" When a new set of fireworks goes up, push the button...when you think you have enough let go. Each exposure was about 4-7 seconds or so.
This set-up will let you enjoy the fireworks and still get great shots.
Also, it's fun to sometimes put the shutter on 1/5 second or so and then set the camera on continuous at 5 frames per second. That will give you what you need to animate a firework set. I only did this once last year but I want to try more this year (unless I am stuck on call can't go
Here is a link to a few shots from last year http://www.flickr.com/photos/bakes/sets/72157605838482991/
Anyways, this worked for me and I got way more shots than I thought I would.