Complete the following achievements to unlock Xbox Live Gamerscore points.

Beat the game once on Recruit or Contractor.

Beat the game on the Recruit difficulty.

Complete the following achievements to unlock Xbox Live Gamerscore points.

Successfully complete the game under the Contractor difficulty setting.

Successfully complete the game under the Operative difficulty setting.

Successfully complete the game under the Professional difficulty setting.

The following achievements require the Veteran Map Pack downloadable content and includes two secret achievements.

The following achievements require the SSC Challenge Map Pack downloadable content.

First Way:
On the last level, (Chapter 6), there is a point where there is a electrical cord that you must pass. You will tell your partner to turn off the electricity flow, so you may get to the other side safely, now after you say this, your partner will quickly run over to the switch, and press it to your command, now, before carrying out the rest of the mission, line up with your partner and push him over the wire, when on the wire, command him to hold position by pressing right on the D-pad, walk back to the switch and press it to restart the flow of electrcity, automatically dowing your partner, press the switch again and the flow of electricity will stop, quickly pick up your partner, and repeat to your heart's desire.

Second Way:
This one is a longer process, but if you don't feel like fighting your way through six levels, it's a lot easier. Just start the game, turn to your partner, and begin firing at him.

Ah, yes, the art of Friendly Fire.

He will respond by returning fire, simply strafe left and right, shooting rapidly, and watch as your partner's health reaches 0, then pick him up, and do it ALL over again.

Use the following trick to earn $1 million in total over the course of Campaign mode. From the main menu, select "Campaign Mode", "Single Player", "Mission Select", then choose the China mission. The first objective pays $30,000 and can be cycled quickly (about three minutes with co-op snipe). The checkpoint is back down the hill next to the hovercraft by the dock. Once you get the checkpoint (which saves your money), quit and restart the mission. Do this as many times as desired.

Keep restarting the Afghanistan level. Four or five martyrs will show up while you are in the back to back. After that, if you restart checkpoint one will appear if you boost up onto the compartment and kill them. Make sure to aim for their chests and not their heads. You can only get the achievement by blowing up the bomb packs on their stomachs.

Start the China mission and complete the first objective for $30,000. After you have successfully completed the objective, quit and reload the mission for another $30,000. You may have to walk back down the mountain for the money to be given to you. This can be redone as many times as desired.

You will get money for picking up a briefcase. Each briefcase can only be collected once and will disappear in future playthroughs. Pause game play and select the "Objective" option to check many briefcases you have collected for the current level. Note: You do not have to collect all briefcase in your first playthrough. You can find missed briefcases during subsequent playthroughs.

Afghanistan:
Look behind the first M-11 missile you find to find a small path going uphill nearby. Follow it to reach the briefcase.

Kill the first heavy armor guard you encounter. After the intermission sequence, search the nearby platform area. The briefcase is on top of a short set of stairs at the back end of the platform.

In the area next to Brian Hick's cell.

Iraq:
Just before climbing up the ladder to take out Ali Youseff's helicopter, get the briefcase at the bottom of the ladder.

Call in the air-strike on a nearby bunker, then search for a large tent near the dividing wall. The briefcase is against the wall near the tent.

Just before meeting Ali Youseff you will see metal platforms with armed guards. Kill all of the guards then climb up the steps to the platform's second level. Climb another ladder to the third level to find the briefcase.

Aircraft Carrier:
Land on the ship's main deck and run to the right of the control tower to find the briefcase.
When you enter the hangar to use one of the parked planes to blow through a door, look behind some missiles to find the briefcase.

After setting the missiles to blow up the ship in the final hangar, search until you find a makeshift basketball court. The briefcase is behind the far basket.

China:
Go to the dam, then move towards the first control tower. Across the dam is another control tower with the briefcase.

Go to the village and co-op snipe some enemies. Follow the rightmost path. Enter the first house you can explore and search the second floor for the briefcase.

Go to the factory, but do not enter. Search behind the factory to find the briefcase.

Miami:
Open the gates to the luggage area then go to the control room. Search the smaller office near the control room to find the briefcase.

Go to the third floor of the SSC Tower. Instead of operating the lift, run to the far end of the third floor to find the briefcase.

When low on ammo on any of your currently-equipped weapons, wait until Mid-Mission Shopping, which is an option multiple times on almost every stage in the game. Change your weapons when this option comes up, and the new gun or guns selected will be fully stocked with ammunition.

Save at least $110,000. Purchase all the masks for one character. As soon as the achievement unlocks, power off your console and start the game again.

You will have both the achievement and the money.

You can easily unlock this achievement during the tutorial stage in Somalia. Hide behind the turret while in full aggro and keep on blind-firing until the achievement unlocks.

You must have a partner that is controlling the second player. To unlock this achievement, your partner should hold the Riot Shield while you're shooting enemies.

Do this in Mission 2 on Casual difficulty. In the part where you'll come out of the lift, have your partner pick up the Riot Shield. Now head to the left path to find most enemies. Kill as much as possible then restart at the checkpoint and repeat the process until you unlock the achievement.

Youll learn from training camp that defeating heavily armored targets require flanking and back-shooting. But what if your partner is pinned, carrying a hostage or regenerating? Simply knock the armored guy down using grenade launchers (barrel upgrade), grenades or some solid firepower. Most of the time, the guy will just roll over, exposing his vulnerable back. Then, move in for the kill.

Throw a grenade in front of your enemy to knock him down. Before he gets back up, either shoot him until he is dead or have the grenade launcher as your frontmount and use one of them to take him out. Depending on the area you are out will change the difficulty of doing this. Remember to use the aggro system to your advantage.

The MSG-90 sniper rifle has a barrel type named "MGS Sniper-Wulf", which is a reference to the Sniper Wolf Boss in Metal Gear Solid.

On Level 5, China, after you blow up the bridge and Alice tells you that your evacuation helicopter is gone, you will resort to the newly-appeared airboat, enter it and travel downstream. There will be a point after a while to your left, with two white water towers with a red tanker docked on the side. Continue down a bit to find an enemy airboat. Do NOT destroy the boat, make it so the AI, or your partner shoots the driver and the gunner only! Get behind it and slowly push it to the back of the tanker, back up and go at it full speed, your boat will flop up, strain the toggle stick up until you are on the dock, then continue on up the hills and...
Wa-La, you are free to roam amongst the hills of China!

In Iraq, when you are told to blow up the bunker there is a glitch that you want to use to your advantage. It works the best on co-op campaign, but single can still help. If you are hurt when you put the beacon in the bunker, after the cut-scene, you will have full health again. The reason this works the best with a co-op campaign is because you can go up to the bunker and have your partner stay down and shoot everyone. When he goes down and needs to be healed, throw the beacon inside the bunker and call in the airstrike. When the cut-scene showing the explosion is finished, you will have full health and your partner will be back on his feet with full health, ready to blast away at more derka-derks.

This when you do the "Man of Many Masks" trick where you'll buy all the masks then as soon as the achievement is unlocked, you'll restart the console to retain the achievement and keep the cash (the masks won't be bought though) After doing this and loading the game, all primary weapons will be unlocked, ready for use. You may now spend your money for upgrades and buying secondary/special weapons.