The keeper should direct traffic and position defenders on the field. Don't expect a lot of this to occur with young keepers, especially those who don't play in goal full time, but with experience a 14 or 15 year old full-time goalkeeper should be able to scan the field and the set the defense as necessary. To do this, the keeper must be a student of the game - they must know:

• The defensive scheme used by the team and how the coach wants the defenders to play
• Tendencies and strengths of the opposing team and opposing players
• The role of first defender, second defender, third defender to make adjustments on the fly
• The role of first, second and third attackers to help anticipate how the attack may develop

In short, they must be a second coach out on the soccer field. This is a tall order for a youth soccer player, but here are a few points that will help develop this.

• Be loud and repetitive. It can be hard to hear out on the field, especially for someone on the ball with their head down. Make sure the message gets through.
• Be specific with commands. Yelling "Mark up!" or "Who's on #23?" often is just not enough - tell specific players what to do ("John, mark #12" or "Jose, Miguel, shift one mark to the right").
• Work from the ball outwards. The keeper should focus on the ball carrier first, and arrange defenders near the ball first. When danger is less imminent, set the defenders who are further away.
• Arrange to get feedback from defenders. It can be eye contact, a wave of the hand, a verbal okay, but have defenders let the goalkeeper know they were heard. The goalkeeper will be able to shift focus knowing the defender is set, and the defender won't have the keeper yelling at them for something they already heard.
• If they keeper does not call, the defenders must take responsibility. The defense should never assume the keeper has a ball unless the keeper calls for it; they should go for the ball unless they hear otherwise. A few collisions with their own defense in practice should quickly teach a quiet keeper the value of calling loudly for the ball!

Communication between the goalkeeper and defenders is a key to making the defense function as a unit.