If you find a room being patrolled by a guard or worker, wait until he leaves, then turn off the light switch. When he returns, he will immediately move to the light switch to turn it on. At this point, his back should be turned to you. Quietly sneak up and either grab or punch him without firing your weapon.
Faster manual lockpick
When using the manual lockpick, instead of rotating it slowly as the game suggests, press the Analog-stick in one of the four diagonal corners, as the "rumble" will always be in one of those directions. This is much quicker.
Always try to stay in shadows or bushes; crouch when walking around; try to take someone hostage before shooting them; always try to use your night vision/thermo goggles just to check to see if there is anything to get around you; and drag bodies into dark corners.
You cannot be seen when hiding in dark places. Shoot the lights to make it dark, but make sure that there are no guards around. Do not stay in the light too long.
Dropping down from high locations silently
If jumping at a place that is a long way down, you will probably die or get hurt. If there is a guard nearby, try to jump down on him so that he takes the damage. Note: You can go into the silent drop while hitting him, so nobody will hear him scream. If there are no guards nearby, go into the silent drop, and when you touch the ground, quickly hold Jump. If done correctly, you will only get about 25% of the damage that you would normally receive by such a drop. You can also land quieter by pressing B (Crouch) immediately before you hit the ground.
Retrieving Sticky Camera
To retrieve a Sticky Camera that is too high to reach, shoot it with the sniper rifle or the handgun. It will fall to the ground.
Knockouts with Sticky Cameras
Use the following trick to have essentially infinite ammunition for knocking out enemies. This does not work until after you have found the SC-20K and have Sticky Cameras. If you are close to an enemy and want to knock him out, shoot him in the head with a Sticky Camera. It will knock out your enemy, and you can then pick the camera up off of the ground. For a convenient attack on a guard or character without being noticed, fire a Sticky Camera (not a Diversion Camera) at your targets' head. Due to gravity, aim slightly higher, near the top of the head or above it. This saves bullets, eliminates the risk of being seen, and you can pick up the cameras and use them again.
If you are pinned down by a turret, throw a flare across it. The turret will be distracted for a moment, which may be long enough for you to sneak behind it and disable it.
Thermal goggle keypad readings
To read the heat signature on a keypad, you can either walk up to the keypad and look at it with the heat goggles on, use sniper mode at a distance with the heat goggles on, or activate the keypad and turn on your heat goggles there. The order of the buttons will be as follows, based on color: Deep Blue, Blue, Light Blue, Green, Light Green, Yellow, Orange, Red. For example, if you had a Deep Blue button at 1, a Light Green button at 3, a Light Blue button at 4, and a Orange-Ish Red button at 6, the code would be 1-4-3-6. This trick where you use your thermal goggles to read the code punched in by a guard is extremely useful, but only available in the second Chinese Embassy mission as the current temperature in the Embassy is low enough for you to notice a difference on the buttons that were pressed by the guard. The buttons go from a deep red color to a deep blue color. Look for the button that is slightly different from most of the other buttons. Then, look for a lighter blue button and so on. following green, yellow, orange and finally red.
If you have someone chasing you, run out a door, and when it closes, stand in front of the door for awhile. The guard will sometimes try to open it before he gives up. Note: The door must open towards you, and not towards the enemy. The game can crash sometimes when you do this. If the guard starts shooting at the door, you must open it quickly. Otherwise, the game will glitch and you will be invisible to the enemy and no event triggers will start.
Disabling Wall Mines
Slowly go up to a Wall Mine. It will flash red and green at an even pace. To disable this, you have to press Action when it flashes green. If it becomes red the instant before you press Action, it will explode. The way to always do this safely is to hold Action button when the "Disable Wall Mine" selection appears. Then, if it is green, release the button. If it is red on the screen, move the selection up to "Back To Game" and try again.
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 also 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.
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.
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.
The Keypad Door: 28469
Mission 1, Police Station
Blaustein's Balcony Door: 091772
Mission 2, Defense Ministry
No keypad doors
Mission 3, Oil Refinery
No keypad doors
Mission 4, CIA HQ
Technical Services Room: 7687
Battery Generator Backup Room: 110598
Storage Room: 2977
Main Server Room: 2019
Weapons Testing Department: 110700
West Entrance to Information Retrieval: 0614
Mission 5, Kalinatek
Security Door: 97531
Archives Department: 33575
Back Door on Third Floor: 1250
Mission 6, Nuclear Power Plant
Cooling Rod Control Room: 560627
Door to Maintenance Shaft: 151822
Maintenance Shaft: 795021
Mission 7, Chinese Embassy
No keypad doors
Mission 8, Abbotoir
Door to Ceiling: 770215
Mission 9, Chinese Embassy
Door to Hall: 1423
Door at Back of Warehouse: 1456
Door to Elevator: 7921
Door to General Keirong's Office: 1836
Mission 10, Presidential Palace
Garden Gate: 2126
Door to Corridor: 70021
Use Sticky Bomb without the Game Boy Advance
During gameplay make sure that your Sticky Bomb is above your SC-20K M.A.W.S (your big gun) on the Inventory List. On any level pick up a can or bottle and go to your Inventory, go to your SC-20K press up on your D-pad (your cross at the left of your controller) press A and you should have the Sticky Bomb on your weapon thing on the bottom right cornor of the screen. You have to press the L button for it to shoot off, then for it to blow up you have to shoot it.
Glitch: Stand on Light
When your in the police station where the jail cells are, go up to the wall and do a wall split.There then should be a light in front of you fall towards it and you'll climb up the light. This is a fun glitch to do.