This bit gives you leadership tips for creating a quiet room so that you can give out instructions.

HAND IN THE AIR
This one comes from my Guiding days. You raise your arm in the air and everyone in the room has to raise their arm, when they do so they have to stand still and be quiet. It can take sometime at the start, I find looking at my watch helps.

WHISTLE
Not a huge fan but might help in a very big space. When you blow a whistle everyone frezzes. When they have stoped blow it agin and everyone sits down.

QUIET SOMEONE IS TALKING.
There is nothing worse than someone talking over the top of a leader. Instead of raising your voice why not start talking very quietly. In most cases whoever was talking will stop to hear what secret is being told.

Get into groups.

In the Games Zone the games involve getting into teams. Here are some ideas to help you do that.

Ask all the players to stand in line in order of ...
Age
Height
House number
Date of birthday
Number of badges (guiding or scouting)
Time they have to get the school bus.
Distance they live from the meeting place.