Do not shoot enemies out of reach
It must have been many of you who
tried to shoot the enemy when far and unaffordable. When you try to shoot the
enemy out of reach, other enemies will hear your weapon's voice and it will
provoke other enemies to know your position and that is very dangerous.
So if you see an enemy that has not seen you yet and you want to get rid of it try to set up tactics to sneak in the right range and then shoot.