You have probably noticed throughout you play, that it is very hard to score goals with headers. The defender's positions seem to be programmed in a way that prevents easy "cross-head-score" combinations. Moreover, when playing against a computer, it is pretty hard to win aerial battles in places other than your own penalty box. So, delivering a goal kick or a long pass with the keeper into the center circle will probably lead to a loss of possession. When your keeper has possession it is advisable to throw the ball to one of your defenders (especially full backs, as there is almost no chance of intercepting the ball on the flank) or to drop the ball to your feet ("Through Ball" button) and start the attack on the ground.