Yes, there are definitely basic skills you must learn before going on particular reality shows. Cindy and Ernie were smart to brush up on many things before going on the Amazing Race. I believe Cindy mentioned they learned two languages, took swimming lessons, and I don't remember what else.
People who are afraid of heights (like me!) need not even bother signing up for The Amazing Race or Fear Factor. You know there's more than likely going to be a heights challenge and you don't want time ticking away while you're confronting a fear that's held you back your whole life.
I still can't get over the number of people who go on Survivor and can't swim or start a fire. I would not only be sure I could do both of those, I would be checking out books about edible plants and anything else I could use to help with the survival aspect. Not that I ever plan to apply for Survivor. Roughing it is not my idea of fun and I'd have no chance of winning the money anyway.