Keep hidden as you proceed to avoid being found by guards, cameras, and sensors.
Enemy soldiers have a 45-degree field of vision. If you enter this field, you will be discovered.
Watch your reactive radar to see enemy movements and keep from being detected. If you're found, you'll need to quickly judge the situation and decide whether to fight or run.
Crawling allows you to hide under tanks, desks, floors, and more. It's a good way to evade enemy pursuit, but if any part of your body is visible, you may still be found.
When you receive a codec call from someone, you'll see the CALL sign. Try to accept these calls as much as you can, as they could provide important advice.
If you use a firearm, the enemy will hear the gunshot/explosion and discover you. When using a handgun or submachine gun, use a suppressor to keep the enemy from hearing gunshots.
Try to keep your ration and ammunition supplies as full as possible for the battles to come.