Holding it, and why your fingertips hurt
Sore fingertips are normal and temporary. A tired wrist is not, and it will not fix itself.
Two things go wrong in the first month, and neither of them is talent.
Your fretting hand is doing more work than it needs to, and your fingertips hurt. The second one is temporary and normal. The first one is worth fixing now, because it quietly limits everything that comes later.
This is step two of the guitar path. Step one was meeting the fretboard.
Sitting with it
Rest the waist of the guitar on your right leg if you are right-handed, with the neck angled slightly upward. Not horizontal, not vertical — somewhere around fifteen or twenty degrees.
Sit up. The moment you hunch to look at your own fingers, your fretting wrist bends further than it should and everything gets harder. You will look at your hands constantly at first, which is fine. Move your eyes, not your spine.
The fretting hand
This is the one that matters, and it comes down to the thumb.
Put your thumb on the back of the neck, roughly behind your middle finger. Not hooked over the top. It will feel less natural and it is immediately more effective, because the thumb and fingers work as opposing halves of a clamp.
Hook it over the top and you have no counterforce. Your fingers end up pressing while your palm rests against the neck, which forces them flat — and flat fingers mute the strings next to the one you meant to play.
Fingers curled, tips down
Come down onto the string with the tip of the finger, with the knuckle bent. Nails short — if you cannot get the tip down because a nail is in the way, that is the whole problem and it takes thirty seconds to fix.
Fingers arrive vertically rather than leaning. A leaning finger touches the string beside it, which is why one string in a chord goes dead and you cannot work out which finger is responsible.
Where the finger lands
Press just behind the fret wire, not in the middle of the space between two frets. This is the single most common cause of buzzing, and it is a placement problem rather than a strength problem.
Try this once: fret a note cleanly, then slowly release pressure until it starts to buzz, then add back the smallest amount that clears it. That is genuinely how much force a note needs. It is far less than most beginners use.
The strumming hand
Less to say, which is itself the point — most early problems are in the other hand.
Hold the pick between thumb and the side of your index finger, with a small amount showing. Grip it loosely enough that a hard strum could knock it out of position. A tight grip produces a harsh sound and a tired forearm.
The motion comes from the wrist, not the elbow. Elbow strumming works for about four bars and then stops being controllable.
Why your fingertips hurt
Because you are pressing thin metal into soft skin, and that skin has not adapted yet.
It lasts about two to three weeks of regular playing. Calluses form, and then it simply stops being a thing you notice. Short daily sessions build them faster and more comfortably than occasional long ones — ten minutes a day beats an hour on Sunday, for your fingertips as much as for your progress.
Do not file or shave calluses off. That is the thing you have been working toward — and it is what makes your first chords stop buzzing.
What is not normal
Pain in the wrist, the thumb joint, or the forearm is a different matter entirely. That is technique, and it does not improve with practice — it gets worse, because practice is repetition of whatever is causing it.
If a position hurts in a joint, stop and change the position. This is the one place where the usual advice about pushing through is actively wrong.
If it is unreasonably hard
Sometimes it is the instrument. High action — the strings sitting too far above the frets — makes everything require more force than it should, and no amount of technique fixes it.
If you have adjusted your hand carefully and the guitar still fights you, it may need a setup rather than more practice. That is a cheap piece of work and it can transform a difficult instrument.
Five minutes
Put one finger on the third fret of the thinnest string, thumb behind the neck, and play it. Adjust until it rings cleanly with the least pressure you can manage.
Then do the same on each of the other five strings, one at a time. That is it. You are not learning a chord — you are finding out what a clean note actually feels like, so you have something to compare against when a chord goes wrong.