This is always worth mentioning to beginners:
Please please please be aware that a huge part of learning guitar falls under the category of PHYSICAL EXERCISE. For your hand in particular but of course for your arms an upper body also. Be aware of your posture. Sit up.pretty straight. Thighs about perpendicular to the floor. And relax. Let your shoulders drop and release any tension from that area. A few deep breaths helps.
As for your hands, those of you just starting out should be aware that many of those bum notes or buzzy noises can be attributed to as-yet unconditioned muscle . Your hand has 34 muscles in the palm – ligaments and tendons running through your fingers.
For most of the time our hands’ daily activities rarely go beyond holding coffee cups, pens, tapping on a screen or a keypad, or turning a page.or two. A guitar asks your hand to apply concentrated pressure over a prolonged period of time, then shift to another position and do the same again. Over and over again. Or in other words, your hand could be forgiven for asking “What the….?”
The strength to do this does not happen overnight. With regular guitar practice – which , as far as your hand is concerned, translates into regular physical exercise, your hand turns into a Schwarzenegger-esque super hand. Your accuracy and finger strength improves, resulting in less buzzes and rattles.
And finally, please do not “play through the pain”. This is not a “no pain no gain” scenario.
Take breaks. Allow your hand to rest. Then resume. And enjoy playing guitar.