The important things are very simple. The simple things are very hard. If you are short of everything except enemy, you are in combat. No combat-ready unit has ever passed inspection. No inspection-ready unit has ever passed combat.
Teamwork is essential.
It gives the enemy more people to shoot at. If the enemy is within range, so are you. Beer math is 2 beers x 37 men - 49 cases. Friendly fire isn't. Anything you do can get you shot, including doing nothing.