Some excellent advice on this thread for any budding night photographer. Especially when it comes to low(ish) iso and shutter speeds if you want good, clear stars, as opposed to streaks.
Sometimes, of course, and especially here in the north of Scotland, all we want are some good clear night skies.
When we do get a good sky and forecast, it's possible to get a good shot at higher iso, this one was taken at 1000 iso, but only to keep the shutter speed shorter.
Canon 5DII, 17-40L, 13 secs, f/4.0, 1000 iso.