Well a tripod helps. You need to experiment a bit with shutter speeds so the brightest beam shot is not over exposed. Then keep the same settings for any other shots.
I did some the other day only to find when I did the brightest light last it was over exposed so I needed to re do them all.
Example
Canon G10
1/50sec
ISO 100
F2.8
Distance from ceiling 2.4 meters
Put it in fully manual mode and make sure if you are taking multiple shots you set the white balance to something other then auto. Don't change any settings between shots.