Use a grid system when organising groups for the practices.
Get the group moving quickly. The warm up phase should be active and must not become boring for the players.
Use clear demonstrations to illustrate the activities. The young players must clearly understand what you want them to do.
Position yourself so that you can see all the players as they work.
When applicable, try to create additional interest by introducing competition between groups or individuals.
If a group has difficulty with one practice, try to modify it using the easier variant of the exercise (you will find an easier and harder variant listed for each exercise). Ensure that there is adequate space to make the practice effective.
Move amongst the groups while they are working. Give praise or advice to individuals and correct errors where appropriate.
Pick out examples of good performance and ask the players concerned to demonstrate them to the rest of the group so as to highlight and develop good practice.