This is a more general rule that applies to betting as a whole. The general theory is that you only make money when the actual odds are wrong. You can only know that the odds are wrong if you know more than the bookies (or find out quicker).
TV betting is a lot less reliant on statistics than other forms of betting. There is not a lot out there at the moment. This makes it difficult for the market makers to compile accurate odds. Usually they just follow Betfairs odds, but that can be a case of compounding mistakes. Betfairs markets are often obviously wrong as well.
So how to find the ricks in the market? Research. Youtube, Facebook, Yahoo Pipes (a current work in progress), Polls, Google, Twitter, Trendrr, Media Outlets, TellyBetting! Pro-punters will study horse form for hours using highly advanced methods so why not TV punters.
Once you have research, try to apply numbers to it. That way you will spot any trends early and this is the key to making regular, reliable money.
So, go hit the books!