4. Decide how much you want to capture
If you really want to capture the individual shell bursts, then you'll want to use a shorter exposure. If you want a photo that gives an idea of the feel and impact of the many bursts going off, go for a longer exposure closer of between 10 and 30 seconds.
5. Have fun with it!
Let's be honest here - if it's not fun, we're probably going to remember that time we ruined the Fourth taking fuzzy pictures. Practice a bit ahead of time by playing around with a slow shutter speed in low light, but remember that it's about capturing the moment and enjoying doing so.