There's not a lot of preparation you need, EXCEPT for having all the info you need for your background check. Start tracking down all the references you need now to fill out that SF-85 or -86, since it can take some time to get it together.
I am doing this the old fashioned way apparently. I have to go the Olathe, KS ARTCC for the interview. I am assuming they will tell me all the info I need to gather for the security check, right?
One more thing. What exactly is entailed in the medical clearance? I fractured my skull, and had a severe concussion, when I was in high school. But it has healed fine with no lasting effects. Will that affect my medical?