You will have players ranging for seasoned rec league participants to soccer first-timers.  Explaining the rules and expectations early on gets everyone on common ground.  This starts with your whistle:

• Tell your team at your first practice what to do when they hear the whistle (start playing or stop and freeze in place).
• Be consistent in using your whistle in all practices.
• Use your whistle when you referee games (6U and 8U only).