Easier aiming with pistol:
To aim better with the pistol, press X 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:
Click the Right Analog-stick to zoom in the sniper scope, then press L 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.

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.

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.

Whistling:
To whistle, press Black. This will usually make a guard approach the sound. Note: Hide in a dark area and whistle, then jump the guard when he stops.

Talking to teammate after losing in multi-player mode 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.

Level select:
When you complete the game on 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.

Defeating Norman Soth:
After you have climbed up the elevator cables and have gotten on top of the other elevator, crawl through the hole in the wall. Norman Soth and two other mercenaries are on the top pathways. While in the hole, there will be one guard on the top path, slightly to the right. You should be able to shoot him in the head. Then, a timer will start and you will have one minute to kill Norman Soth and his other mercenary. When you shoot the first mercenary, drop out of the hole onto the first pathway. The second mercenary will go to exactly where the you shot the first mercenary. Shoot the second mercenary in the head. Note: The second guard will be aiming at the hole, so he will not see you if you drop out of the hole. The last person to kill is Normon Soth. Start running down the pathway and turn left on the second to last walkway on the left. Look up and turn on your thermal vision. You will see Normon Soth. Get a clear shot and shoot him in the head. After that you must retrieve the smallpox box from the top pathway. If you are on the second to last pathway on the left, go up the ladder. There will be another ladder; use it to climb up. Drop off the ledge onto the pathway. Run down the middle pathway to find the smallpox box.

Capturing Suhadi Sadono:
After killing off all of Sadono's guards, lure him into a dark corner then shoot him with a Ring Airfoil. Then, run up behind him and grab him. You can now force him to use the retinal scanner and complete the mission. Also, rather than picking off each one of the bodyguards, you can go to the right all the way around the room in the shadows. You should then reach the stage behind Sadono. Follow the curtain's shadow to Sadono. There will be a gap. Stand up and run until you see the "Grab Character" option appear. Grab him. You will be shot at and probably get hit, but once you grab him they will stop and you will hear someone say "Don't shoot, you might hurt Sadono". After that you are home free as they will not follow you.

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. Also 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.