Over at the Tricks of the Trade weblog, advice for listeners trying to win that radio station contest:
Radio hosts prefer winners who sound excited. So if you call a station and sound fun, there's a better chance of not only winning but getting on air as well. The whole "caller 9" thing is mostly a filtering trick, allowing the host to tell boring-sounding people "you're caller number 7, sorry.
What? I really wasn't number 7?
Radio Personality [Tricks of the Trade]