from what i have experienced so far of PES10, it is important to time headers to get maximum effect.
i think they can become more advanced though
when two people are challenging for the ball in the air (currently), only one player actually jumps for the ball. both players should jump for the ball, and, no matter which of the two players wins the header, the ball should go off target slightly (whether a shot at goal or pass to a team-mate), as the second player pressurises the attacker of the ball.
also, if a player has high aggression (for example), the harder he tries to attack a ball in the air (ie, the longer you keep hold of X,O, triangle or square), the more likely he is to elbow an opponent challenging for the same ball, and may earn himself a yellow card if he tries too hard!
i think they can become more advanced though
when two people are challenging for the ball in the air (currently), only one player actually jumps for the ball. both players should jump for the ball, and, no matter which of the two players wins the header, the ball should go off target slightly (whether a shot at goal or pass to a team-mate), as the second player pressurises the attacker of the ball.
also, if a player has high aggression (for example), the harder he tries to attack a ball in the air (ie, the longer you keep hold of X,O, triangle or square), the more likely he is to elbow an opponent challenging for the same ball, and may earn himself a yellow card if he tries too hard!