If you work at a desk job, most likely your shoulders will be tight from the hours of sitting at a desk over a computer. When your shoulders are tight, then you cannot make a full shoulder turn and this may lead to swing faults. Bicycle arms is an excellent exercise that will not only loosen muscles but will help you develop strength and endurance.

Stand in a shoulder width stance holding a golf club parallel to the ground.
Rotate the club forward as if you were peddling a bicycle with your hands and arms, taking your shoulders through full range of motion.
Rotate forward for 8 to 10 repetitions and then rotate back for 8 to 10 repetitions.