I've found accumulators (called multi-bets at TAB) are pretty good value - where you select more than one bet, multiplying the odds each time, and it pays off if all of them occur. There's not much to it really, if you can bet online just look through the various games and pick a few things you think are likely. You can start with outright results (Brazil and Italy to win or something), and move on to other things like first goalscorer, halftime/fulltime doubles, exact scores and so on. My two biggest wins so far have come on accumulators where I picked several results in the same day, including an exact score in one of them.
It can also be a good idea to put a bit of your money on a fairly safe bet, in the (likely) occurance that the others don't work out. I started with $25 a few days back, and put half of it on Sweden to beat Paraguay. When that happened, I had a bit more to work with the next day.
Knowing your luck in the prediction thread, you'll be a millionaire in no time.