Lock in focus, and find the right light balance
On your phone, tap and hold the area you want to be in focus, then slide up or down to adjust the exposure
...But avoid a long exposure
Although shooting in low light typically requires a long exposure, you’ll want to shoot the moon just as you would an object during daylight. That’s because if you leave the shutter open for too long, you won’t be able to capture the interesting detail of the moon’s surface, and instead will just get an bright orb.
Use a tripod
For a crystal clear snap, you’ll want to keep your camera/phone super stabilized. If you don’t have access to a tripod, find a solid surface to rest your camera on, and shoot using a timer. If there’s no surface in sight and you must shoot with your camera in-hand, there's a trick to use your body as a tripod and reduce accidental body shaking or movement when you snap the pic: hold your breath, hoisting your camera in position with your elbows firm against your sides, then tap the shutter.