Pinning Enemies and Ammunition

Use high-explosive grenades to finish off injured, pinned-down enemies

Grenades are good for softening up the enemy before a charge. They really come into their own, though, when you're fighting against an enemy at moderate distance who has already taken some damage. If he has nowhere to run, then you can toss a HE grenade right into his lap and there's little he can do about it. It is particularly effective when your target is in a confined area where they cannot move about much. Corner them, pin them down, injure them, and then finish them off with a grenade.

Switch to sidearm when out of ammunition in a firefight

Out of ammunition with your primary weapon? Switch to your sidearm, or, in the worst case, your knife. Practice this; if you know you're about to have an encounter with an enemy around the corner and already have a few rounds left in your primary, switch to your sidearm early so that you don't waste time switching mid-fight. If you get caught reloading, you can still switch to your sidearm (although obviously your reload won't have completed so your primary will still be out of ammo). Be ready to switch to your sidearm at a moment's notice.