Extreme Mode
Beat the whole game in any difficulty to get Extreme Mode.

Beat tanks
Tanks are a problem when they are facing you the best way to take em down is to throw a smoke grenade at the tank(if the 50 cal is shooting at you)aim your LAW or anti tank weapon at the bottom center of it so its nearly going under the tank. if done correctly the tank will be destroyed.

Extra supplies
When you run out of medic packs or ammo, don't pull out the knife. that will be hard to kill the enemy and it will lower your health. Try to find enemy buildings or bases that you already cleared out and look for guns and ammo. Most of the time there will be rocket launchers, ammo, guns and medic packs.

Destroy Scuds with a grenade
Have a grenade and throw it by or under the door of the scud, and should by destroyed.

Wrench
As you cycle through Jones weapons you will find a wrench you can use it to fix a jeep, tank, or your Bradley fighting vehicle and keep it running instead of being destroyed. Note: once your vehicle is destroyed it wont work

Level 2 the unknown tank before the mortar team
The unknown tank is located before the mortar team. You can get a an anti-tank rocket in side the building where u see the tank head on.
Remember you only have 2 shots with the anti-tank rocket so AIM IT PERFECTLY OR YOU WONT HAVE ENOUGH ROCKETS!!!

Third Level
Here's a tip for the 3rd level, stock up on anti- tank rockets, and anything explosive. At the end of the level you have to protect Delta Squad and its chopper from all side. Including snipers, solider, and tanks of all kinds!

Stealth on mission 4
On the 4th level, after you drive up to the mines and get out, be Foley, and go up the little ledge. Command your men to stay back. Then, just take out all of the guys you can see. Foley has a silenced sniper rifle on this level so they won't notice you unless they see you. Try to make all of your shots head shots or upper torso shots. You'll know when you've killed every guy in that area because it will say "Objective Completed"