Lack of flexibility in the hips causes you to straighten your spine and bring your pelvis underneath your body on the backswing
One reason for Jack Nicklaus' greatness can be traced to the meticulous nature of his set up routine when he picked and focused on his intermediate target
An inside out swing approaches the ball on the downswing from too low, hitting the half of the ball closer to the player, causing a push or hook which requires the player to work on getting the club further up and out on the downswing