On July 4th, we had gone to see the fireworks display at Pier 39. It was pretty good, but personally, I was disappointed that it lasted only for 30 minutes.
Nevertheless, here are a few things that helped me photograph the event. Hope it is useful to you too.
1. Use a tripod
Since you will be photographing primarily in the night and shutter speeds will drop to several seconds, you just cannot do without a sturdy tripod.
2. Use a low ISO value
Since you have a tripod, and since you need slightly longer shutter speed to capture the firework trails, use a low ISO value.
3. Aperture of f11-16 works best for me
Wider than F11, the light at the middle could be blown out. Narrower than F16, you could have diffusion issues depending on your lens. F11-16 works best for me.
4. Shoot manual
Go to manual mode. With the aperture mentioned above, you should be able to click at 4 seconds or so and get a decent light trail of the bursting cracker. Depending on the firework, you could get a very nice streak of light.
Focusing in the dark could be an issue. Few like to focus on infinity and shoot. However, I waited for the first firework burst, when it turned bright, focussed on it and then turned auto-focus off. Until I changed my focal length, I used the same focus. However, you need to be careful not to accidentally turn the focus ring to offset it.
6. Compensate for the fluorescent colors of the crackers
You may perhaps like to use a warm flourescent light white balance if the crackers used tend to emit strong flourescent colors. Of course, shooting in raw will help you play with multiple white balance options.
7. Mirror lock-up mode with remote release
To avoid shutter release vibration, use the mirror lockup mode and trigger the shutter using the remote. You could also use the 2sec timed release option in your camera if you do not have a remote.
8. If light is too blown out even at low ISO and F16ish apertures, use neutral density filters
Use neutral density filters. If the burst happens in the top portion of the frame, perhaps a 2-3 stop gnd could help.
9. Time the burst
Note down how many seconds every burst and its light trail lasts. Try to match the full duration of the burst trail to get proper trail streaks.
10. Try to shoot when the wind is calm
When the wind is strong, clicking a picture could mean that the streak trails could be blown away by wind causing a fading light blur which you may or may not like. If you want a proper trail, try to click when the wind is calmer.
11. Turn off noise reduction in your camera
If your camera has noise reduction feature turned on, you could spend quite a bit of time between shots when the camera is busy working on the noise reduction (this is why clicking a long exposure could take a long time before camera is ready for next click).