The lit parts of the moon are essentially at the same distance from the sun as we are, so the daylight exposure setting (sunny-16 rule) would be a starting point. Depending on the altitude of the moon relative to the horizon, and atmospheric conditions, there may be some light extinction, so if it is too dark, you start opening things up. I use the native ISO (in my case 100), use an f/stop which is sharp with my lens (since I probably don't need a deep DOF unless I'm shooting the foreground as well), put my camera on a tripod, and shoot at 1/400 sec or so at f/8. IF, on the other hand, I want to capture the earth-glow on the moon, then that is anywhere from 6-8 stops dimmer. In practice, an exposure about 4 stops dimmer will keep the earth-glow dark, but not black, which is the effect that I would normally want.