Read the manual.
Sometime on the 4th there appeared on the Yahoo main page a link to an article on how to take great firework photographs.
Now granted, fireworks are not something you get to run out and shoot at a moment's notice, and they do take some planning, but I've tried my hand at it now and again.
One of my previous best attempts is here, taken 4 years ago in the summer of '03, a long way away from the fireworks and with a much more inferior camera. Most of the images from that night are blurred and after a review today, I trashed almost all of them.
The article said to use a tripod. Well, I did that.
The article also said to use a long exposure, or even hold the exposure open manually (bulb setting if your camera has it) by using a shutter release.
So when, to my surprise, fireworks appeared right of my balcony, I ran and got the camera, tripod and shutter release and decided to see what a long exposure would do - in the neighborhood of 5 - 13 seconds. In order to compensate for the long exposure I also reduced the aperture to f16.
It turned out that for the big finish I should have made adjustments, but there was no time, and the final photos are overpowered with light.
But overall, I'm happy with the results.
You can read the article here.