Shooting fireworks can be a lot of fun and can produce some very interesting images. I usually like to keep my ISO low (100) and experiment with different f/stops & shutter speeds depending on the effect I am looking for. This image was shot on Manual at f/3.2 at 1/60th of second with an ISO of 100. Try to focus on something in the distant background using manual focus. If you want longer trails, use a longer shutter speed. For shorter trails use a shorter shutter speed.
Don’t worry about your light meter as it will be tricked by the dark sky and tend to overexpose. Try different settings and review your LCD to preview your images. You may want to use a tripod to steady your camera if there are buildings, lakes, etc. in your shot. Shoot LOTS of photos to make sure you get some heroes!
Oh yeah, leave your flash OFF!