The fundamentals of a golf swing are the grip, aim, stance, and posture.
If you play right-handed, place your right hand on top and the left hand on the bottom. Turn your left hand so you can see two and a half knuckles of your left hand. The top of your left thumb should rest under the thumb of the right hand. Point the right thumb diagonally across the club. The index finger and thumb on each hand form two V shapes. The V's on each hand should point to your right shoulder.
Grip the club before you aim so adjusting the aim doesn't change the grip.
The stance is distance between your feet and the position of the ball relative to your feet. A good stance balances stability and mobility.
The posture is the flex in your upper body over your waist, the flex in the knees, the distribution of your weight on each foot. During the backswing, the weight should remain on the inside of your feet to avoid sliding.