Standard Rules of Combat-
1. If you can keep your head while those around you are losing theirs, you may have misjudged the situation.
2. The enemy of my enemy is my enemy's enemy, no more, no less.
3. There is no "overkill". There is only "open fire" and "reload".
4. Anything worth fighting for is worth fighting dirty for.
5. If your attack is going really well, it's an ambush.
6. When in doubt, empty your magazine.
7. Fair fights don't exist. There's always an edge. If you don't have it, they do.
8. Teamwork is essential; it gives the enemy other people to call primary.