Rifle rapid-fire:
Equip the rifle and press L3. The bullets on the screen will be a bit darker. This indicates that you have switched to rapid-fire mode. Be careful, as you cannot simply hold the trigger as you could before; the gun will shoot as much until you release.

Better sniper mode accuracy:
For better accuracy on sniper mode, hold L1. Note: This may take a few seconds to start.

Escaping a room full of soldiers:
Take a sticky camera or smoke grenades and throw it near where the most guards are located. For the sticky camera, a control bar that tells you how to make a noise or use smoke will appear at the bottom of the screen. Throw the smoke grenade and the smoke should knock out some guards. When the smoke appears from the grenade(s), it is your chance to run for it .

Knock out an enemy:
To knock out an enemy without killing him, equip the sticky camera and shoot it at his head. Aim slightly above the head to compensate for gravity. After he is down, pick up the sticky camera and use it again.

You can throw bottles to knock out guards. You must aim and hit them in the head.

Taking out two guards:
Shoot a sticky camera near the guard closest to you. When he approaches, use the gas to knock him out. The other guard will approach to investigate. You must either shoot him with a non lethal round if you cannot have casualties, or take him out with a head shot if killing is sanctioned. This has to be done correctly or he will revive the guard that you knocked out.

Eliminating guard threat without ammunition:
If you do not have ammunition and you find two guards, sneak up to one and take him hostage. Make sure that your hostage is facing the other guard or he will shoot you.

If you do not have ammunition, hide in the shadows and wait for a guard to come up to you (or slowly creep up to him) then press R1 to punch him. Use two punches to knock out someone.

If you need to knock out many guards without killing them, look around for a water puddle. Try to lure them into it, then shoot a Sticky Shocker into the water. This will knock many of them out. This works with any body of water, including the sewers in the Chinese Embassy level.

Luring your enemy:
To do this, find a can or glass bottle to pick up. Once obtained, move to a location, preferably dark. While hidden, throw the can or bottle to an open area with an enemy nearby. When thrown, the enemy will wonder what happened and walk towards that location. After you have drawn him out, you can take him out for an easy kill.

Hiding bodies:
After you have disposed of enemies in an area, make sure that you still hide them, even though no one is nearby. Before going to another checkpoint, the alarm may ring, and it will say that a body was found. Try to hide all bodies in hidden areas for best results.

Quickly drop body:
When moving a body. equip your weapon. This will automatically drop the body.

Hide face:
Have the diversionary camera equipped with the SC-10. Press L1 button before you zoom in and fire it at a wall. If Sam is close to the wall, he will put his hand in front of the camera to hide his face. You can try this with any sticky camera, but you need to be close to the wall you shoot it on for him to cover it.

Keypad codes:

Mission 1 - Police Station
Keypad 1: 091772
Keypad 2: 5929

Mission 4 - CIA HQ
Keypad 1: 7687
Keypad 2: 110598
Keypad 3: 2019
Keypad 4: 110700
Keypad 5: 0614 (if Dougherty gets through the door before you can)

Mission 5 - Kalinatek
Keypad 1: 97531
Keypad 2: 33575
Keypad 3: 1250

Mission 8 - Chinese Embassy, Part II
Keypad 1: 1436
Keypad 2: 9753
Keypad 3: 1456
Keypad 4: 1834
Keypad 5: 7921

Mission 9 - Presidential Palace
Keypad 1: 2126
Keypad 2: 70021
Keypad 3: 66768