The simple things are always hard. When you have secured the area, don't forget to tell the enemy. Incoming fire has the right of way. No combat-ready unit has ever passed inspection. No inspection-ready unit has ever passed combat.
Teamwork is essential.
It gives the enemy other people to shoot at. If the enemy is in range so are you. Friendly fire isn't. Anything you do can get you shot including doing nothing. Make it too tough for the enemy to get in and you can't get out.