What is the best method for filming fireworks?

Should I set it to "auto", "spotlight" or "night" mode?

I've only got one chance at it tonight, and perhaps tomorrow night (Plymouth Fireworks Competition), so I really want to get it right first time. Last nights filming was a disaster.

Focussing on fireworks displays won't work, because of their transient nature. So I've already decided to set the camera to record at "infinity".

Only a few hours to go, so does anyone have any tips on videoing fireworks gratefully received.

Thanks.