Not sure about using the d70 but my other camera i used something like F8 manual focus, need a tripod and a remote shutter if you have one with you D70 that is fine, if not use the timer. I would try different time upto about 5 secs maybe but i always had a hat so used to cover the lens with the shutter open while in bulb
mode, then when i heard the burst i would take the hat away. It's all trial and error but once u have it focused in the first shots thats it no need to touch it again. Using the remote or the timer is a must to avoid camera shake. Hope this helps a bit.
Our Fireworks only goes for about 10 minutes so i no sooner got the hang of it and was all over.
This was my first ever fireworks shot, oh and yeh dont be dwnwind from the smoke.
Not the greatest shot, but was ok for first time and we only have them once a year here.
Cheers
John
BBJ