Long exposure star trail photography?

What is a setting i should have my camera on for a successful shot? (i have a nikon d3000)

And roughly how long will this photo take?

First, you must have a tripod for star trail photography.

Second, this site will give you the guidance you need: http://www.danheller.com/star-trails

Shoot as long as you want, the longer you go, the longer the trail.

You need a dark area, because any light pollution or lit up areas near the ground will start to dominate the image. Moonless nights are the best. You also need a tripod to hold the camera steady. You also need a remote release to hold the shutter open.

If you have an interval times, you can set the camera to take 100s of fast images and use software to stack them. This is the easiest way to get the dark part of the sky to stay dark and avoid issues with light pollution, but it requires extra equipment.

Without an interval times, you manually focus the lens to infinity, set the shutter speed to B (bulb), open the aperture to f/8 or so, and hold the shutter open for as long as you want, hours if you have the battery life for it.

Here are a couple of web resources:

http://pinterest.com/...339919335/
http://www.mikesalway.com.au/tag/nightscape-photography-101/