How to Photograph Fireworks
Use a tripod - Long exposures are needed to capture the fireworks. Trying to shoot without a tripod will result in blurry, unusable images.
Use a shutter cable - Using the shutter button on your camera body may cause very small vibrations, blurring your photo. Use a shutter cable to alleviate the potential problem.
Kill the flash - Using your flash will do nothing but kill your batteries..and possibly light up unwanted subjects (people, trees, animals, evil gnomes)
Shutter Speed - Use a shutter speed ranging from one to five seconds.
Aperture - Set your f/ stop to anywhere between f/8 and f/16.
ISO - Keep your ISO setting low. Ideally, ISO100 is perfect.
Focal Length - If you want to include the surrounding area in your shot (water, city skyline, etc), use a wider angle lens, somewhere between 18 and 50mm. If you just want the fireworks in your photo, I recommend at least a minimum of 100-200mm depending on your distance to the show.
Experiment - Try different settings until you find the ones that suit what you are looking for. Write them down or enter them into your smartphone just in case you accidently change something.
Check the weather - You would think this is a no brainer. Not only do you need to check for rain, but also wind direction. Ideally you want to shoot up wind if possible. If the wind is calm, it is best to shoot the beginning of the show. As the display goes on, the smoke from the fireworks will hang in the air, making it difficult to get quality photos.
Focus - Remember to focus before the show. Nothing is more irritating than taking what you think are amazing photos only to get home and find out that they are all out of focus. Set you lens to infinity or find something close to where the fireworks will be shot from and focus on that. Then switch to manual focus so the lens won’t try to refocus after every shot.