Presents some technical challenges,learning how to photograph fireworks successfully needs quite a different approach to most other subjects but follow these few steps carefully and you will be successful. What are we photographing? Basically we are photographing streaks of light that develop over a period of time against a black background. The great thing about a black background is that it makes no impression on the film, or sensor in the case of a digital camera. So we can leave the shutter open as long as we like, the black will still be black.
So, in short, the way to photograph fireworks is to set the camera to manual exposure (or use a old analog camera), set the aperture to a suitable f-stop and the shutter to 'b' or bulb. Open the shutter just before the firework bursts and close it after it's finished. Easy!
The first thing we need is a sturdy tripod. The alternative methods of support that I mentioned in the photographing buildings tutorial won't cut it here. Here we are talking about seriously long shutter times of several seconds so nothing but a good sturdy tripod will do. The second piece of kit that would be very useful is a remote shutter release so you don't have to touch the camera at all. In the old days this was a cheap piece of kit called a cable release but nowadays it is more likely to be an electronic gizmo with a higher price tag. I, personally, don't use one but that's because I'm a cheapskate.
I'm afraid all the modes and settings that you paid all that money for are all useless when photographing fireworks and auto focus is one of them. If you leave your camera set to auto focus the lens will whirr backwards and forwards in a demented fashion trying to find something to focus on in the black sky.
Set the focus to manual and then focus on something in the far distance. Don't just wind the focus ring around to the end of its run, check it against a distant object if you can.