When shooting the moon, remember that it is being illuminated by the same sun that gives us "daylight" , even though it is usually surrounded by dark sky. So an appropriate exposure is usually in the daylight range. Following the sunny 16 rule, that's 1/100 sec at f/16 at ISO 100. However, the amount of light lost by passage through the atmosphere will usually require a stop or two more exposure to compensate. In addition, the natural albedo of the mood is equivalent to black asphalt, yet we are used to seeing it bright, so we in effect have to overexpose it to get the naturally dark moon to appear bright. So adding these considerations to the exposure calculation, a starting point may be something like 1/100 at f/5.6 at ISO 100.
If you're shooting only the moon, with no foreground, then you don't need to have a high aperture value as you don't need the depth-of-field, so a value like f/4 or f/5.6 would be appropriate, depending on your lens.
The shutter speed will need to compensate for any lens magnification you're using, as well as the moon's apparent movement across the sky. Here the usual guideline of using at least the minimum shutter speed (reciprocal of the focal length, more or less) for the focal length is appropriate. So If you're shooting a full-frame with a 100 mm lens, then a minimum shutter speed of about 1/100 sec. would be a starting point. If you're using a 200mm lens, then the minimum would be 1/200 sec. If you're using a crop camera, then the shutter speed should be decreased by the crop factor. This is if you're shooting hand-held.
The better way of shooting the moon is to put the camera on a tripod. That gives you some flexibility with respect to the shutter speeds you choose, because it eliminates camera movement/shake that is inherent in hand-held shots.
A very common reason for blurry moon shots is missed focus. Relying on the camera's AF mechanism often does NOT work, so the usual method is to switch the focus mechanism to manual. Since the moon is essentially at infinity, you can manually set the lens to infinity, if your lens shows the infinity point. If not, another method is to use the live-view function (again, manual focus). Still another method is to focus on some very distant point on earth, lock the focus, and then aim at the moon.
Still another contributor to blurry shots is the image-stabilization of the camera or lens. It does not help if your camera is on a tripod, or if your shutter speed is sufficiently high.
When I take moon shots, I usually use the tripod and a remote shutter (to minimize camera vibration), image stabilization is off, focus is manually acquired using Live-view with magnification, exposure is manually set using the calculation given earlier, and then adjusted up or down after the first (test) exposure, aperture is usually around f/4 or f/5.6.
Hope this helps.