I agree with most of the responses so far... more or less.
The moon reflects sunlight, absorbing a bit. On a clear night, a "correct" exposure of it is usually one to two stops more than a "full sun" photo would be. So, you can start out with the "sunny 16 rule" and simply adjust a little from there...
Sunny 16 tells us that in full sun you'll get a pretty accurate exposure if you set your aperture to f16, and then your shutter speed to the reciprocal of your ISO sensitivity. So, for example, you would use ISO 100, 1/100 shutter speed and f16 to shoot a brightly sunlit scene. You can adjust any one of these settings by similarly tweaking one or both of the other settings... For example, f11, ISO 100 and 1/200 would give you the same exposure... Or f8, ISO 50 and 1/200 also would achieve the same.
Now, the moon isn't quite as bright as full sun. Not all the sunlight that's falling on it is reflected toward us. Some is absorbed by the moon's surface, some is filtered by our own atmosphere and some is reflected other directions. So try "Moony 8" instead. Using f8, 1/100 and ISO 100 will give you two stops more exposure than "Sunny 16" and should get you in the ballpark.
You'll likely not be able to use any of your camera's auto exposure modes, because the bright moon in a dark expanse will very likely end up very over-exposed. A manual setting carefully done is more likely to get you a correct exposure.
But, there are other things to consider:
For one, as mentioned, the moon is moving. Actually it's surprisingly fast, though we don't normally notice it. Yes, 1/100 or 1/125 is about as slow a shutter speed you'll want to use, or you'll get subject movement blur. But faster might be better. You'll most likely be using a fairly powerful telephoto to shoot the moon, so a very steady tripod and slightly faster shutter speed can help. For especially long telephotos, also consider other tricks to get a steady shots... such as using a remote release and mirror lockup (a short self-timer delay and Live View shooting can do much the same things). Also it can help to add some weight hanging below the tripod and/or lay a beanbag on top the camera and lens (both limited by the practical weight capacity of your tripod, of course). A windless evening and steady ground (i.e., not a wood deck or the deck of a boat!) also may be helpful.
You also want to be careful not to use too small an aperture. Super small apertures cause a optical effect called "diffraction", that robs fine detail from your images and that might particularly be a problem with a moon shot. f8 and f11 are pretty safe with most digitals. But f16 and f22 can cause too much loss of fine detail. Read more about diffraction here:
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htmManual focus might be the way to go, but it's generally not as simple as setting it all the way to infinity. To understand why, read up on hyperfocal distances:
http://www.cambridgeincolour.com/tutorials/hyperfocal-distance.htmI also suggest you might want to time your shots...Often it's better to shoot the moon at dusk or dawn, rather than in the middle of the night. This way the sky still has a little light in it, both for a more interesting shot and because contrast isn't so strong as it is later when the sky is fully dark. If you prefer a more colorless sky, with digital it's easy to change the color, de-saturate it or darken it later in post-processing.
It also may help to shoot the moon when it's low on the horizon, as it tends to be "magnified" when shooting it through more atmosphere. It also can make for a lot more interesting moon shot if there is something in the fore-ground, rather than it high in the sky. But you really need to weigh this against other considerations, such as the clarity of the atmosphere when you're shooting. a lot of air-borne dust or heat distortions can seriously deteriorate image quality (...or might make for an interesting shot... depending upon your goals).
There also are certain times when the moon is nearer or farther from the Earth. It's orbit around us isn't a precise circle, but more of an elipse. "Super moons" occur occasionally and might be special opportunities for photographers.
Lunar eclipses can be interesting too... just remember that once it's partially obscured by the shadow of the Earth, a bit of additional exposure is likely to be needed.
Online you can find moonrise, moonset, Super Moon, eclipse and other important timing info calculated for your particular longitude and latitude. Of course, anywhere you're shooting you'll still be at the mercy of the weather, ambient light conditions and other things.