Level select:
When you complete the game under the normal or hard difficulty setting, when you go back into the game make sure you go over towards the level select instead of checkpoints. You could lose your data and have to do it over again if the wrong choice is made.

Underground radio:
During the Kundang Camp level, you will eventually end up chasing Sadono underground. Your CO will advise you that they will no longer be able to communicate with you while you are underground, due to interference from copper. However, if you get caught by a guard or an alarm is sounded, your CO will be able come over your earpiece saying that you need to watch the alarms. The female counterpart will also say something, even though they are not supposed to be able to reach you.

Easier aiming with pistol:
To aim better with the pistol, press Square to pull it out. The crosshair should appear normal. Then, press Up on the D-pad and the crosshair should become a laser sight. This makes it very easy to aim, since the laser sight is smaller and thinner than the normal crosshair. This allows fast kills and head shots. Note: If you are in dark corners and have the laser sight on, the enemies will notice and attack you.

Easier aiming with SC-20K:
Press R3 to zoom in the sniper scope, then press L1 to hold your breath. You should be able to get a good shot while Sam remains still.

Knocking out guards:
To knock out a guard without using a Sticky Shocker or a Air Foil, shoot a Sticky Cam at their head. Note: It must hit him directly in the head for the guard to get knocked out.

Television Free: Drowning your victims:
In Television Free (mission 8), you will have a chance to go down into the sewer. When you knock out a guard, drag their unconscious body into the water then click into thermal view. You can watch the life slowly slip out of their bodies.

Stealth:
To move quieter, crouch down and walk slower. This will make your steps softer, and keep you undetected to a limit.

To decrease your chances of being seen, shoot out the lights with your gun. Be careful, as if there is an enemy is under that light they may see you shooting it out.

Shoot without fear:
When you are at a point that you can only use non-lethal attacks, make sure that you have the SC-20K and at least one Sticky Cam. Instead of waiting to sneak up on a person, shoot them in the head with the Sticky-Cam. This knocks them out without using "lethal methods". Aiming high is the key to knocking the person out because the Sticky Cams have a short range. After the attack you can pick your cam up and use it again.

Bypassing motion detectors:
Before passing by a motion detector, pick up the body of a dead or unconscious guard. Then, proceed to walk past the motion detector. The motion detector should not go off, due to it seeing the guard on your shoulders, thus making you invisible to it.

Find mines easily:
In order to find mines in the camp mission, turn on the thermal vision.

Multiplayer: Talking to teammate after losing:
When you are playing in an online match and lose all of your respawn lives, mute your teammate and then unmute him. Both of you can now communicate with each other.

Prince Of Persia references:
On the mission when you are on the train, look in the second car where the guard is located. Knock him out then go behind the fenced door. Look down you will see a magazine featuring Prince Of Persia.

On the third level when you are in Paris on the train, at the beginning there will be a room with an engineer. Knock him out. On the floor of the room is a Prince Of Persia strategy guide.

Various references:
On the first half of the Jerusalem level, there is a book store directly behind an alley with a swinging lamp. Next to it is another smaller alley with a swinging lamp. If you look inside the large window you can see many different picture references to The Punisher, Ubi Soft's XIII, an anime, and a picture of the infamous "Sniper Kitty" among many other things. Use the binoculars to get a much better look.