I have a fantastic series of confidence building drills here for you to follow.
But first... it is important to work on individual soccer drills with all players. Attackers, defenders, and goalies all should be comfortable and confident on the ball when performing the soccer moves and exercises.
It is never too young to begin to work on these, but bear in mind the age group and simply guide your practice plans accordingly. Players should have a ball at their feet as much as possible during training to develop this area of the game.
There are lots of simple, fun soccer games you can do with the young beginners, and as players mature there are plenty of more competitive, challenging drills.
As often as possible! I can recollect very few practices when growing up where my coach didn't begin each session with at least one taught skill to improve our individual abilities. Repetition is key to allow players to have the necessary confidence on the ball.
A coach should bear in mind the age and skill level of each player and adjust the individual drills to match. Then as the players confidence increases, so too will their ability to focus and concentrate on the game at hand rather than worrying if they are doing the right pass or dribbling okay.
Here are some individual soccer exercises to enjoy:
Square Drill Foot Skills
Soccer Converge Drill
Quick Thinking for Footwork
Shielding Soccer Ball
Quick Feet Ball Control
Figure Eight Dribbling
Box Cross Ball Skills
1v1 with Defender
Criss Cross Dribbling
Change of Pace Speed Soccer