Put something else in the frame as a reference rather than just fireworks.
I see everyone post that a tri-pod is a must but I don't think a little blur will ruin the pics if you hand hold.
Use a slow shutter speed and try to get the initial rising trail in the exposure as well.
In post-processing... duplicate the original layer, blur, lighten and blend to Overlay (if anyone needs more detail on this I'll add it in... bit of a rush now).
If I had the time and resources I think I would look for a glass high-rise building and shoot the building as the fireworks reflect off of it. I'm not near buildings like that but if anyone can use that idea (assuming it's a good one) by all means.
I have several fireworks shots that I do believe came out quite well (especially seeing as at this point, I did not understand too much about exposure). From what I remember, these were shot with TV ranging anywhere from 1/4s to 1/15s, generally with an aperture around 4.0. Since I didn't bring a tripod, I ended up laying down with my head propped up with a bag and just shot to my hearts content. Sorry that I can't be of much help.