Fireworks shots can be tricky. It requires timing and technique in order to get it right.
First, you'll probably want to stop down to f/8 or something like that. Fireworks are bright, and they will easily blow past your sensor's dynamic range if you leave the aperture at 2.8 and expose for a while.
Expose for more than a second. At one second, unless your timing is really, really good, you'll only get about half of any given burst. 2.5 or even 5 seconds is the right amount.
Because you'll be exposing for a long time, make sure to use a tripod. If you don't use a tripod, you still have to stabilize your camera; no stabilization makes for wonky trails effects.
If you can, try to frame the firework with something else. The shots I took yesterday didn't have anything to really frame with, except in one shot, by a lucky accident.
With that having been said, enjoy!
I like this shot, although you can see the need for a tripod here. Problem is, a lot of these shots were fairly well stabilized (even though a stroller hardly qualifies as particularly stable), so I can't really be sure if the jitters in this image are from wind or from the camera moving. Usually, when all the trails of the fireworks move together, it's from camera movement, but I don't think that's what happened here. I may be just fooling myself because I like the shot.
This last shot showed some very interesting postprocessing recovery. I don't know if the thumbnail production on the Dp2 is just really bad compared to the raw output, but the following image was just a mass of white where the large burst is. But, because I shot in raw, that white was easily recovered into some very cool trails:
And finally, the serendipetous shot of someone else in the crowd chimping. I would say something snarky like "Firewroks Watching: Yer doin' it wrong!", but I was guilty myself of chimping a fair share throughout the show.
