My tips... use a tripod and take a longer exposure at a lower ISO setting to capture the bloom of the fireworks. You can even use a neutral density filter to get an even longer exposure. And don't worry if you have a point and shoot, you can still get some good fireworks shots if you use that tripod.
though I totally disregarded that advice with this one. It was shot hand held with a 50D at ISO 6400 using a 50mm f/1.8 lens.

This shot was with a tripod and a point and shoot on AUTO...








