So far, my calls have displayed, what I think economists call, diminishing returns.
First, I was told by Tom that I made a home run with my (on topic) call saying that the show "Two and a Half Men" would work better as a cereal commercial.
Second, acquitted myself un-embarrassingly whilst ranting about the last Indiana Jones movie.
Then, a really sad call offering a just terribly awkward lyric for that Ted Leo and The Pharmacists song about the world going into the terlet. (The lesson to me from this call is this: Sometimes, you may wind up on hold for such a long time that your idea's moment will have passed by. My advice in this situation is cut your losses and hang up.)
And most recently tonight, which I don't want to think about too much (a kind of ill-conceived effort to volunteer reporting on the Mighty Boosh Bash).
The moral of the story is: If you are nervous about calling in, wait for a topic you can nail and call on topic. Don't let the fact that you've listened to the show a lot and/or have exchanged a few emails with the host lull you into lazy or overly casual chumminess. This is the Best Show, so you have to rise to the occasion a bit and/or at least be humble.
Alternately, you can just blither through and keep shamelessly calling until you get a weird familial or bar-regular type status.