How to shoot pictures of stars with a nikon dslr?

Nikon d3000

Point the camera upward at night.

You will need a tripod and turn on the NR (noise reduction) for both long exposures and high ISO settings.

After that all you can to is experiment for the best exposure.

This usually works best if you set up your camera miles from any city or villages where there no light pollution and when shooting on cool clear nights

Just like with any dSLR. See settings on example below.

http://keerok-potd.blogspot.com/2012/02/polaris.html

Set the white balance to daylight. At ISO 400, 15 seconds f3.5 you should see all the stars your eye could see and more. At 18mm 15 seconds star trailing won't seem very noticeable, but by 30 seconds it can be.
Under a full moon (like tonight) about 30 seconds, f3.5, ISO 400 should make your scene look almost like daylight, except for stars in the sky.
A tricky part is getting the camera to focus. It helps to have a tripod with a quick release plate to make it easy to take it off and put it back on as you try to get the camera focused. You need your autofocus to lock onto something, and then switch to manual without disturbing the setting. A distant street light might work. Maybe pointing your car's headlights at something can get you an adequate target.
Turning up the ISO may not be very helpful, as noise can get very high. You are more likely to be seeing noise mottling than any interstellar nebulosities.

Start with a well charged battery, and bring a spare. Long exposures can drain batteries a lot.