Use the lens wide open. The combination of focal length, aperture, and film speed (and brightness of your local sky) will determine how many stars are visible as trails [*]. The length of your exposure determines not how many stars are visible, but how long the trails are. A trail will rotate 15 degrees around the pole in 1 hour, so if you want short arcs you can go for say 20-30 minutes, but longer arcs need an hour or more. If your local sky isn't really dark, long exposures will bring up the sky level noticeably.
To accentuate the curvature of trails, point closer to a pole, eg north in the Northern hemisphere, even if you don't include the pole. Pointing at the celestial equator could be neat but the arcs will be less apparently curved.
Color film brings out colors in the stars (and the sky glow) that are not visible to the naked eye.
For obvious reasons, any moon beyond a thin crescent will bring up the sky brightness a lot, so you want to work with the moon down when possible. However, if the moon is low on the horizon during your exposure, it won't affect the sky brightness much, and the moonlight gently illuminating the foreground can be interesting. (It can be a warm color at moonrise/set, like sunrise/set, because moonlight is a similar color to sunlight, which is physically reasonable but conceptually difficult for people because we are trained to think of moonlight as "cold.")
[*] A technical note for people who really care: for normal photography, exposure sensitivity depends on aperture and not focal length; but for star photography, focal length also matters because stars are unresolved point sources, not areas of a defined surface brightness.
