fireworks are a strange subject. getting the technique right is one aspect, after that, i quickly got bored with it and wanted to do some images instead. the only solution is to include some of the environment, for me, reflections (if on water), but not only. i am honestly quite bored with my own shots, so tkae that into account when evaluating my advice.
a few points about technique: if you expect to be close to "ground zero" (as in, less than a few hundred meters), get a wideangle, or even ultrawide too, you might need it. scout the location in advance (one hour at least, i would say, depends how well you know the location already), try to compose some imaginary shots, and chose a spot that seems to work for you. some things most people don't "get": you can control how birght the streaks are with aperture/iso, not with shutter speed (unless you are going for frozen action, no streaks), you will quickly learn by feel if you need to open up or close, and roughly how much, when you see the firework burst and see how birght it is, they can vary wildly depending on the complexity of the show. if you use very long exposure times (what this means depends on how abundent the show is at that particular time), shutter speed will matter to some extent (because of overlaping of succesive fireworks). the exposure time will affect the brightness of the environment, though, which will most likely be lit by the fireworks themselves, so if you care about that, you will need to juggle with those settings a bit. you might want to deactivate dark frame substraction if you are using a k10d, you cannot if you are using a k20d, this will enable you to react faster (no wait time between shots). set the camera on a tripod, and look at the show while you shoot, trying to anticipate and decide when to pull the trigger, don't look through the viewfinder, at least not too much, get a remote (cable) release if possible (more confortable), turn
sr off, don't use shutter delay to get mirro lock up (you'll have to make do without mlu). check the shots from time to time on the lcd, turn on the blinking of highlights (saves a lot of time) and the "quick zoom" (if using a k10d or k20d). finally, keep in mind nights can be colder than you might think (depending on your area), and especially so by the water, keep in mind you will be standing still for a long while.
have fun
edit: examples, fwiw
