How to avoid star trails?

I know that star trails are often an element of a photo that is intended, but what if we want to capture a landscape at night without the trails, just the stars. Something like this: a href="http://bit.ly/cidFSZ," rel="nofollow"http://bit.ly/cidFSZ,/a where the stars are static, or this: a href="http://bit.ly/aMFV0z" rel="nofollow"http://bit.ly/aMFV0z/a (there is actually a shore in the bottom of this photo). So, what are the techniques for avoiding star trails. Are there certain tricks with the aperture, ISO, and exposure time that I don't know yet. Or is there an efficient way to eliminate star trails on a computer.