The club is in contact with your head throughout the whole trick, but for most of the time you can't see it because it is out of your field of vision; for this reason a mirror can sometimes help for the initial stages of practice. When you position the club against your head, the knob should be about level with your mouth and your hand should be at the top of the handle near to where it joins the body. Practice will tell you how much of a push to give it. Experiment by rolling the club over different parts of your head, for me it works better near the front rather than right over the crown.
The catch is made with the club upside down and the palm of your hand facing the front. When you bring your hand down in front of you the club should be the right way up again. Cartwheels look good when done continuously from one hand or when mixed in with other head tricks.