Your posture is determined by your arm swing. If you swing up and down on a two plane swing then you should stand more upright. If you swing your arms around on a one plane swing then stand more bent over on the balls of your feet.
Match the movement of the club with the movement of the body to arrive back at the same point
On the course you should focus on simple thoughts when you swing, generally keeping to one thought per round but rotating through them each round