Relax Your Wrist to Help Clean Up Your Guitar Chords
Beginning guitar players have an impulse to grip the guitar neck tightly with the fretting hand- the hand that holds down the chord shapes. Your fingers feel clumsy and weak when you first start playing, so there's a tendency to want to add strength from the hand, wrist, maybe the forearm. But tensing the wrist and jamming your hand against the guitar neck tires out your fretting hand and messes up your sound. It causes you to mute (deaden) strings that should ring out clearly.
Relaxing the wrist is one of the most helpful tips for beginners or frustrated guitar players because it accomplishes two important things at once. First, it moves your palm away from the neck of the guitar so the high E string can ring out clearly. It also gets your thumb out of the way, putting it somewhere on the back of the guitar neck. The pad of the thumb should rest comfortably, without tension, against the back of the guitar neck to avoid deadening the low E string. When you relax your wrist, that happens automatically.
There will be plenty of times in your guitar-playing life when you'll want to mute the high E or low E string on purpose, but there are better ways than jamming your wrist against the guitar neck. As a new player trying to build your skills, make sure your wrist hangs loose.
Give it a try now and watch what happens. Play an Em, Am, C, D- whatever. If your hand and wrist are crowding the guitar neck, relax your wrist and let it hang loose. Notice how this automatically puts some space between the palm of your hand and the neck of your guitar so the high E string rings out clearly. Watch how this adjustment, relaxing the wrist, shifts your thumb to a comfortable position on the back of the guitar neck, too.
Relaxing your wrist is the most efficient way to shift the workload to the fingers where it belongs.