First and foremost dealing with crosses is very much a psychological strength, so when dealing with a cross or coaching your Goalkeeping to deal with a cross everything must be positive!!
I always start by taking the pressure off them, as a goalkeepers first fear is always dropping or missing a cross, leading to the ball going in the back of the net, this fear transfers to negativity which intern leads them to fall deeper into their goal, drops the team deeper on top of him/her making it even harder for them to come and catch a cross.
Young Goalkeepers should be encouraged to enjoy taking crosses, adopting good, positive starting positions in relation to the ball. Be Confident, bold and brave!!
Adopting high, positive starting positions will not only encourage the Goalkeeper to come and take more crosses it will enable the back four to defend higher, allowing more space for the goalkeeper to attack the ball. With the Goalkeeper adopting a higher starting position and being positive with decisions the wingers will be more obliged to cross the ball further away from goal.
Being in positive positions in and around the goal will create positive decisions, whereas negative positions will automatically create negative decisions!