1 Tripod or anything stable you can set your camera on. Such as a fence, a bag, a truck/car hood. You will not be able to hold your camera and get crisp pictures!
2 ISO Even though it’s at night time that you are shooting your light source (fireworks) are going to be bright. So having a lower ISO will be ideal. So start with 100 or even 200.
3 Aperture keep it all in focus with a lower aperture. Maybe start around f/5.6 or f/8 to test out your landscape focus.
4 Shutter Speed Here is the tricky part. You want to keep your shutter speed open a bit longer than you probably normally do. You might have to take a few trial and error shots before you really nail it! Remember the longer you leave it open like 3-4 seconds you will get the milky streamy light streaks. If you go for a quicker shutter speed like 1 second or less you will get a crisper feel to your light streaks!
5 No FLASH If you use your pop up flash it’s not going to work. You cannot use that at all!
6 Focus if you find your camera won’t focus on the firework light consider switching your lens to manual focus and trying to manually focus on your subject.
7 Arrive Early It’s always wise to arrive early, get your best spot and do some test shots!!! If you’re like me this kind of photography I don’t do it every day, so sometimes having a few minutes without the pressure really helps me to get my settings where I am comfortable!