Capturing Fireworks is difficult for several reasons, the foremost being that the occasions are rare making opportunities to practice and learn limited. Similarly, fireworks shows are popular events so finding the right location that allows for optimal settings are frequently crowded and not always easy to get your gear in place; but with planning, it can be done!
As for the mechanics of actually capturing good photos of fireworks displays; this is a challenge but also a fun time to experiment and learn more about your camera. While you’ll be shooting at night, the fireworks are quite bright so you shouldn’t have too much trouble getting an exposure that captures the light. The real challenge comes in capturing the essence of the display; the rise of the firework, the explosion and the aftermath occur with irregular cadence and random duration; not to mention the location (height of explosion) and the size (width) will also vary. Set yourself up for success by not over-zooming (you can always tighten up on the explosions in development). Even though it will be dark avoid the temptation to open the aperture too wide. A wide aperture could given you a depth of field challenge. Keep the ISO low, in the 200-400 range.
With F-stop in the mid-to-high range and ISO low, the setting to throttle is shutter speed, but in this case the throttling will be done with a special piece of equipment, a manual shutter release cable. The shutter release cable allows you to manually control the opening and closing of the shutter from less than a second to several seconds allowing more light to be captured on your sensor. In the case of fireworks, a manual shutter release allows you to determine in real-time how much of the actual explosion you want to capture effectively allowing you to record the essence of the firework - the spiraling rise, the initial burst, the falling glowing elements, and the change in colors can all be recorded by the duration of the exposure that you (vice a set camera speed rating) are directly controlling. It takes some practice, but it is well worth the effort. This is where your creative abilities really come into play.
The manual shutter release cable makes a tripod a must. You physically can’t juggle all of these items, and even if you could, your photos would be jumbled and disjointed. Make sure the tripod is on firm ground (even add weights to the tripod legs in order to minimize shake from local accidental movement) and use your manual release cable. These cables can be specific to the brand of camera, but considering other photography equipment prices, these are relatively inexpensive.
Composition & Planning Considerations In choosing the right location consider the following:
Where will fireworks explode, what will be in the way (trees, buildings, crowds)?
Are there monuments or buildings you want in the foreground/background (helps viewer recall the event, but also relates the size and magnitude of the displays)?
Which way is the winding blowing? Note the direction of the wind prevailing wind? Watch that the smoke doesn’t blow onto your location and cloud the shots.
Can I get all of my equipment and kit to the location?
Will the moon be out and where will it be in the night sky (consult online tables)?
What time is the display?
Tripod (and possibly weights)
Manual shutter release cable
Zoom lens - for getting in tight
Lens filters - to remove glare if needed
Glow sticks - mark the legs of your tripod so no-one unwittingly tramps through your equipment
Blanket and chairs - general comfort - prepare to wait...