Use your OCGs (Optical Camouflage Generators) as much as possible when in an enemy-filled area. They will not be able to see you, giving you the upper hand. You will then be able to destroy them without them even knowing you are there. If you like to shoot extra items such as cars, stacks of cans, etc., do not do so when an enemy is near, as they can "see" the fire. If you get shot when your OCGs are on, they will turn off and the enemy will be able to see you. Go into hiding if they need to recharge.