The first thing to consider is location. Ideally you want to be some distance away from the action. Some fireworks fly up over 200m, and then burst over a very wide area, but they can also fly in unpredictable directions. If you're too close then you're going to have to move the camera quickly to capture the burst, which will prove to be very difficult if not impossible. By standing back from the action you should be able to fit every likely trajectory and burst diameter in the frame without too much trouble. Obviously this is going to be easier at an organised firework show in a larger venue than it is in your back garden.
If you're shooting fireworks on Guy Fawkes Night in the UK, bear in mind it's probably going to be pretty cold outside, so it's a good idea to take your camera outside for half an hour or so before you expect to be taking photos. If you take a camera straight outside from a warm room into the cold night air you may experience problems with condensation on the lens, which will cause blurring as well as reducing contrast and colour saturation. If you give your camera time to cool down to the outside temperature this is less likely to happen. See this tutorial for tips on using your camera in cold weather.
Set your tripod up so that you have a good view, but take care to avoid people tripping over it in the dark. If you're at an organised firework display try and stay at the back of the crowd. If it's a big display then there probably won't be much going on at ground level anyway, since all the fireworks will be ignited electronically, so there's not much point in getting to the front.
If you're at a smaller bonfire party, don't forget to take photos of other things than just the main fireworks. Sparklers look great at shutter speeds of around a quarter of a second. The better image stabilisation systems will allow you to take reasonably decent hand-held shots at that sort of speed, but it's still a better idea to use a tripod.