Please forgive me for crashing your board, but I tend to win radio contests somewhat regularly. (I'm guessing that, if you have to keep track of the "only once every 30 days" rule, that's regularly)
Anyhow, if you really want to win, put the number on Speed Dial, and start calling when you even suspect they're about to announce the call in! If they're taking caller #10, and they answer with "you're #3" - hang up & hit redial or your speed dial number! If the caller number is 15 or under, keep dialing through 2 songs, then give up if you haven't won. I've never been able to gauge the Caller #90 ones, but I think you get the idea. If you get the funny busy signal (Buzz-buzz-buzz) that means there's a winner, so give up.
Think positive, think lucky, and when you win, enthuse a LOT!!! They WANT people who get excited about winning!
FYI - the radio station I listen to was taking only 15 callers for a home improvement prize package that they'll draw on Monday - and I'm one of them!! So, anyone who wants to wish me some luck, I sure could use it!
Good luck with your contest!!