Use the height advantage of your arms. If the attacker is well outside on the flank, start near the far post so that you can keep track of the action and where players are. If the attacker cuts in towards the near post, then move more towards the near post yourself as you will have less time to come forward

Once the ball is crossed in, if you can reach the ball safely (there aren't too many players in your way and you are close enough to it's path) then you must attack it. If you aren't sure, stay put and prepare for a shot. If you decide to go, go all out with the mindset that you must get the ball no matter what.

Take off on one foot and time the ball to get it at it's highest possible point so as to prevent an attacker from reaching it with their head.

Secure the ball to your body for safety as you land. Concentrate and do not let yourself be distracted by anything. Once you have the ball secure, immediately look for an outlet throw or punt to your team to start a counter-attack.