You must be able to handle a variety of move orders during the first 5-6 moves - otherwise you'll find yourself 'tricked' time and time again.
Edmar MednisBobby Fischer started off each game with a great advantage: after the opening he had used less time than his opponent and thus had more time available later on. The major reason why he never had serious time pressure was that his rapid opening play simply left sufficient time for the middlegame.
Edmar Mednis