Never share a foxhole with anyone braver than yourself. If you are short of everything but the enemy, you're in contact. When you have secured an area, don't forget to tell the enemy. Radios will fail as soon as you desperately need fire support. The only thing more accurate than incoming fire is incoming friendly fire.
Tracers work both ways.
When in doubt empty the magazine. If you are a grunt in the desert, you can run but you'll just die tired. Have your musket clean as a whistle, hatched scoured, sixty rounds powder and ball, and be ready to march at a minute's warning. When you're on the march, act the way you would if you was sneaking up on a deer. See the enemy first.