When you're new to golf it seems as if a million things are happening all at once. Your mind is full of thoughts about setup, swing plane, rhythm, balance, hip turn and other variables. But golf swings aren't really that difficult. Your goal is simply to create a lot of clubhead speed and transfer that speed to the ball. The way you do that is no different than in any other sport.
The first step is to turn your shoulders more than your hips. This is your backswing, and this shoulder/hip "separation" is familiar to anyone who ever has swung a baseball bat or thrown a Frisbee. Ideally, you'd like to turn enough that your back faces your target while your hips turn a little less than half that much. From this position you can make a huge swing arc with your hands and club, and that's a key to hitting long, powerful shots.
At the top of your backswing your wrists will cock the club, the same way a batter cocks his wrists to set the bat in place. The wrists remain as relaxed as possible during the swing, and the change of direction at the top helps set the club for the downswing. In fact, it's the club's resistance to changing direction that keeps your wrists cocked until your hands are in the hitting area at the bottom of the downswing.
Hit Down on the Ball
You need the ball to get up in the air if it's going to fly a long way. When you swing properly, your wrists stay cocked most of the way down to the ball. This "delayed release" of your wrists means that the club shaft suddenly snaps back into the ball at impact, creating a downward blow where the clubhead strikes the ball before it hits the ground. The downward blow compresses the ball against the ground, causing it to shoot out with backspin and climb into the air with a lot of velocity.
If you were to simply stop your body at the moment the club strikes the ball, you'd probably never hit your target. To keep the club traveling down your target line you need to let your body continue rotating into a full finish with your hands over your shoulder. This lets you impart every bit of clubhead speed you can into the shot. It keeps the clubhead square to the clubhead's swing path, ensuring that the ball starts out on its intended line. And it gives the club time to slow down without hurting you. When it's done, a good swing leaves you in a balanced finish position.