It looks like this topic is pretty old but just to put any doubts to rest, SF SGT is right.
Forget any rumors or anything you've seen in movies because it is most likely wrong. Most people like to talk about things they have no clue about.
Firstly, you do not need to be tabbed in any way to join their organization. If you want to be a support guy there then the only real requirement is that you volunteer for Airborne School and of course make it through their selection process. If you want to be an Operator then that's a different matter and requires a bit more work. A background in combat arms or special operations is a plus, but you can be a cook and become an operator if you have what they're looking for (though it's not likely).
Secondly, CAG is not looking to mold, teach, or train a guy into being a stud. If you do not already possess the appropriate physical fitness, intelligence level, maturity, and attitude that they expect, then you'll be wasting everyone's time by applying. The thing that people need to keep in mind is that CAG is not a job or MOS. Being that level of an Operator is a way of life. You don't just punch out at the end of the day. So if you're a PFC who played some Medal Of Honor game and wanted to try it out for real, you might want to do a little research and check yourself.
"Relax, sir. It's an SF thing."