1. Use a tripod.
2. Use a cable release so you can watch the firework rocket trajectory with both eyes on the sky.
3. Use a zoom lens - 70 to 200 mm or more unless you need to capture the background.
4. Put the camera on manual and set the Shutter Speed for around 4 seconds and aperture of f 11.
5. Manual focus to infinity.
6. ISO 200.
7. Take an interesting background exposure - more wide angle. Use this as your background layer in Photoshop.
8. In Photoshop, choose your background image and then the other single fireworks images and adjust each in Camera RAW. Open your background image first. Use the Lasso tool (L) to select areas to use of each individual fireworks images and with the Move tool (V) drag each onto a new layer above your background image.
9. Blend each layer with Lighten.
10. Re-position each display (on its own layer) with the Move tool (V) as needed.
11. Then use the hi pass filter to sharpen as needed. (Flatten and then Duplicate the background layer, then select Filter, Other, Hi Pass filter, adjust for thin white lines, then select the Overlay Blend Mode).
This new technique worked better for me then the bulb with the black card I had used in the past.

Triple FireworksIn camera triple fireworks exposure over the harbor.

12. Try in camera triple exposures if you have a Nikon DSLR - keep on auto gain. See above.

Fireworks over the NeckFireworks over the harbor and the neck.

Fireworks over Gloucester HarborFirework montage over harbor waters. The year's 4th of July photo montages from our July 3rd Gloucester fireworks.  Enjoy.