It's mid-winter here and I started dreaming about warmer days and then about fireworks photography. Here are some simple rules I use to take pictures of fireworks.
Use a wide angle lens, manual camera, low ISO, long shutter speed (4 to 10 seconds or more), cable release, tripod, and focus on infinity. If taking video, be sure to use a stabilizer of some sort (tripod, mechanical stabilizer, table, post, etc). A cell phone works for video just fine.
Be sure to look for unusual pictures - fireworks shows have lots of other interesting things that make great pictures.
Ask for permission to get some unusual shots (sometimes you can place a camera in the field - or have a technician do it for you).
Be nice to those around you! Don't block someone's view.