Mr Felix try doing a search on the rule of 600 for doing star shots. It works really well and have done it many times myself. It does require knowing where infinity is on your lens but you can work that out easily enough even with the kit lenses.
Basically you;
- Set f/stop wide open
- ISO to 2000 to 4000
- To calc the shutter speed take the focal length then calculate 600 / focal length
- Focus to infinity
- Ensure you've got mirror lock up on and are either using timer or a shutter release