1. Practice should be fun.
Concentrate on the fun factor. Skip "drills" and lead activities and games. Limit dead time....let them play.
2. Be all about skill development.
At least 80% of the practice players should have the ball at their feet. Focus on technique.
3. Positive Motivation is important
Encourage, Encourage, Encourage.
4. Have efficient, effective trainings.
Plan your practices, have maximum amount of touches on the ball, limit the lines kids are standing in, try to make it one ball per player until free play (scrimmage).
(ideas borrowed from David Huddleston, April 2012)