I prefer "bulb" mode to "manual" mode (I believe some cameras don't have a separate mode for bulb, but set it as a shutter speed instead.)
The big difference here is that
you determine how long you want your shot to be. For example, you can start the shot during one particular burst and stop when it's done, not when the camera's done. Example:
The thing that makes this a little different is that because you don't know what the shutter speed will be, you can't perfectly predict the exposure. This is OK IMHO, because the very nature of fireworks means that exposure changes
dramatically from one moment to the next. If there are many fireworks going off at once, you take a shorter picture... and if it's a quieter moment, you can hold the shutter open longer. Of course, with the castle in the foreground, there will be times when the castle is properly exposed and the fireworks are over or underexposed, and times when the fireworks are perfect but the castle is over or underexposed. This is, again, unavoidable due to the ever-changing light. Here's an example of a nicely exposed castle and overexposed fireworks.
Here's one with a slightly underexposed castle but more properly exposed fireworks.
Of course, this technique pretty much requires a remote shutter release. I was able to set the camera on the tripod before the fireworks, then just stand back and hit the button on the remote to fire off the shots, no need to even check the viewfinder. The camera itself was set for F8 and ISO 200 and manually focused.
One thing to also think about is maybe trying to shoot from a different location. The obvious place is right center in front of the castle, but I've seen some really interesting photos from other angles. Next trip, I hope to take some from behind the castle - say, Tomorrowland or Frontierland. You can also get some neat photos completely
outside the MK. These are from the beach at the Polynesian - we weren't staying, we just visited one night.
Also - most of these techniques are assuming that you're trying to shoot Wishes (or Remember... Dreams Come True), but they should work fine for any fireworks, including Illuminations - but that one is a bit trickier as you're closer to the action, so if using a tripod, you either need a very wide lens, or you may want to re-frame the camera sometimes, to capture the fireworks at water level or the ones in the sky.