Another excellent tutorial from Digital Camera World

Shooting at night has been a technique that many photographers have used to give their landscapes and cityscapes an otherworldly appearance.
But it has usually involved very long exposures, leading to star trails or light trails. The improved high ISO performance of modern digital SLRs means that it’s possible to get amazing results without resorting to long exposures, keeping the stars and other moving objects sharp.
Skills involved
Shooting in the dark makes it tricky to focus and frame your shot accurately, so you’ll need to practise these skills before you head out to shoot starscapes.
Switching your camera to manual focus and using Live View can help, as it’s often possible to see the subject more clearly than by using the viewfinder. Use the Manual exposure mode.
Take some test shots to arrive at the best settings to use for your shots, as the brightness of the stars and the amount of light pollution will vary in different locations.
The technique
To capture the best starscapes you’ll need a completely clear sky, so check the weather forecast before heading out. It’s best if the moon isn’t visible: it can make it difficult to keep detail in the whole sky in a single exposure.
To keep the exposures short enough to prevent the moving stars blurring, set a high ISO such as 1,600 or 3,200. Even then, you’ll need a wide aperture: f/4 or even f/2.8.
This means it’s almost impossible to keep both the stars and any foreground subject in focus in a single shot. Shoot two exposures, one focused on the stars and one on the foreground, then combine them in Photoshop.
Creative photo effects: 01 Use perspective to fool the viewer
Creative photo effects: 02 How to make a spherical panorama in minutes
Creative Photo Effects: 03 How to capture motion blur without using a tripod
Creative Photo Effects: 04 Capture great bokeh with ease
Creative Photo Effects: 05 Replicate a tilt-shift effect
Creative Photo Effects: 06 Use lens flare creatively
Creative Photo Effects: 07 How to underexpose the background for dramatic effect
Creative Photo Effects: 08 How to make realistic HDR