First you'll need a tripod. Night photography is all about long exposures. You'll need to have your camera in Manual Mode since you'll be in control.

I use and recommend the FotoSharp "Day & Night Exposure Guide". Here are a few examples:

Scene 45 minutes after sunset; Indoor sports, circus - floodlit; Brightly lit street corners

ISO 100
f4 @ 1/8 sec.
f5.6 @ 1/4 sec.
f8 @ 1/2 sec.
f11 @ 1 sec.

Floodlit buildings, fountains; Outdoor Christmas lights; Candlelight close-ups

ISO 100
f4 @ 1 sec.
f5.6 @ 2 sec.
f8 @ 4 sec.
f11 @ 8 sec.

City skyline in distance

ISO 100
f4 @ 8 sec.
f5.6 @ 15 sec.
f8 @ 30 sec.
f11 @ 1 min.

See? No need for a high ISO or a wide-open lens or guessing at exposures.