What camera do you have? I like using ISO 100 to reduce noise, and doing very long exposures. I've since read that doing multiple shorter exposures over the same time period and then stacking them can give better (less noisy) photos however. But, in that case you will have a lot of files on the memory card instead of just one. I usually shoot at whatever the lens is sharpest at, usually ~f/8. On my 20D I would put it on a tripod and have a remote shutter button, set it to bulb time and click the bulb and I'd go to sleep and check the camera in the morning. That would get me about a 2.5 hour exposure before the battery died. I tried doing this on my 7D but the battery lasts a lot longer, so I ended up running into the early morning sky, which washed away the stars. So for my 7D now I set my remote shutter/intervalometer to hold the shutter for about 3 hours.
If you do the multiple exposure things and then stack them afterwards, that also leaves you with the opportunity to create a time lapse. But if you shoot in RAW and take a bunch of exposures with an intervalometer, this is going to use a LOT of space. Also one thing you may run into issues with if the temperature changes a bit during the night is condensation on the front lens element. Also, pay attention to where the north star is (or the southern cross) depending on which hemisphere you will be in, because the stars will appear to rotate about that point, so that will help you compose your shot.
I just realized I don't have any of my starscape photos on my Flickr to give you examples! I'll have to get those off my external drive and uploaded!
Also, one of the main reasons I upgraded from my 20D to my 7D was my hope that I could take less noisy starscapes. With long exposures and my 20D I would get red pixels in many different parts of the image. Not sure what camera you have, but when I first opened my 7D, it had one red pixel when I would take a photo with the lens cap on. I was so mad until I figured out that if you run the "manual sensor cleaning" for a couple minutes and then turn the camera off and back on, it fixes it. If your camera has this feature, make sure to do that.
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