1. You do tell everyone about Pillow Fight.
2. You do TELL EVERYONE about Pillow Fight.
3. Bring a Pillow.
4. If someone whines or has no pillow, you cannot hit them.
5. Everyone with a pillow joins in the fight.
6. The pillow fight starts at the designated time - No earlier.
7. Nothing in your pillow but PILLOW.
8. Pillow Fights will go on until they're done, (though apparently there is a whistle this time?).

...and as mz.chief points out, take away as much pillow as you brought.