The goalkeepers are the last line of defense and a very important link in a soccer team. Their job is certainly one of the toughest on the pitch, since their mistakes are a lot more visible than the mistakes of their fellow field players. Goalkeeping has changed a lot since the days of Sepp Maier and Lev Yashin. Modern goalkeepers have more attributions than just preventing the ball from passing the goal-line. They are called into action more often as they sometimes need to act as sweepers. Nowadays a good keeper is also a good defense coordinator.
Positioning is essential when it comes to goaltending as they have to know exactly where they are at all times. Goalies need to comprehend the tactics of the sport and know how to read the play. All these require thorough specific goalkeeping training.
The goalkeeper has to keep his eyes on the ball at all times. Understanding how to cut angles is an important skill to learn for any goalkeeper, therefore the goalie should be instructed to do so as if he had a string attached to their back from the center of the goal. This is a great mental drill.
One simple drill is to have a few players, spread all over the pitch, shoot or cross in quick succession. The keepers are required to move fast across the goal while maintaining the perfect position to stop the ball, catch it or dive quickly to both the left and right.
Another important goalkeeping skill is communication. Yes, being vocal in the goal area is a fundamental skill. Modern goalkeeping requires knowing how to control a defense. Good communication not only saves the goalie from having to face one on one situations but also provides a great moral boost for the defenders. For a goalie, telling your teammates that they're doing a great job, and encouraging them is absolutely necessary even though they're only doing what they're supposed to do. We all need our work acknowledged. Not being able to communicate with the defenders is bound to have serious repercussions. There's no special drill to improve a goalkeeper's communication skill, he just has to be himself, keep composure and advice the defense whenever he thinks he's reading the situation better.