There is a truck by an entrance to the missile building. Get on the hood and crouch, then turn left then right while still crouching. You will eventually be able to get inside. You can walk around in the truck. You can see and shoot out of it, but your opponents cannot. Do not throw grenades or they can shoot your feet. You should stand behind a wheel. Those are the only parts of the truck you can see.
Go to the large tower, then g by the stairs and get in between the yellow poles. Use your knife and drop on the skinny wall. Knife the wall. When you see a small part of the underground, run toward it to go underground. Note: This works best during Spy Hunt mode.
This hidden location is recommended when on Team Bravo. Go up the main body of the cargo plane and turn left to the tail section. You should see one of the tail rudders hidden by some branches. Go to that side and you will be in a hidden location. Use a silenced weapon or else you'll be spotted. You can also crouch for added protection.
It is possible to set off a grenade as it flies through the air. This can be very effective whenever your team gets pinned by someone spamming grenades everywhere. Look up and whenever there is a grenade in the air coming towards you, fire at it. This causes it to explode in the sky. Note: This can be difficult to do.
Crawl between the remains of what appear to be two tanks. If you crouch into the correct location you will start to fall. Once you start to fall, tap W + S repeatedly. You should become invincible and invisible.
-Jump on top of an enemy's head and kill them, then stand still. If they do not immediately move when they respawn, you will be on their head again, allowing you to kill them easily once more.
-Try to surprise your enemies instead of camping and waiting for them to move in your direction. This is a great way of defeating your opponent. When you see your opponent moving in a specific direction, always go the other way while being unseen as you backstab them. Note: Using a knife is recommended.