Try to look unimportant; they may be low on ammo.
Never share a foxhole with anyone braver than you are.
There are no aethists in foxholes.
Professional soldiers are predictable, but the world is full of amateurs.
The easy way is always mined.
The only thing more accurate than incoming enemy fire is incoming friendly fire.
When you have secured an area, don't forget to tell the enemy.
If your attack is going really well, it's an ambush.
Make it too tough for the enemy to get in and you can't get out.
A Purple Heart just proves that you were smart enough to think of a plan, stupid enough to try it, and lucky enough to survive. (But not smart enough to duck.)
It is generally inadvisable to eject directly over the area you just bombed.
When the pin is pulled, Mr. Grenade is not our friend.
If the enemy is in range,so are you.
If you are short of everything except enemy, you are in combat.
But then everyday life is often like combat. And these rules are easily adapted for everyday life.