Advanced holdem strategy will advise to use pre-flop betting to get profitable returns. Poker school will teach you the basics of a raise or fold game, which is fine if you want to try and stay in the game and play conservative poker. However, playing this way will sometimes earn you very little return, as the blinds eat into your stack and you wait for the good cards to come along.
Try mix in some aggressive play, like pre-flop raising and re-raising, it will get your opponents to think twice about challenging you and committing chips. Its really difficult to stand up to a player that is coming at you aggressively and you are either, not in a position to counter them or you do not have the cards, to take them on. The correct use of pre-flop betting will increase your returns in the poker room.
Over use of the pre-flop bet will start to raise suspicions so use it with care, otherwise players will get suspicious and start calling you.