-Full Guide- ***Spoilers*** in case you are just doing veteran straight away...freak :P.
You start on a helicopter waiting to infiltrate a cargo ship.
1. NO KNOWN DANGER
When you drop rope down, just stand there. If you feel unsecure then take cover but the AI will kill them all.
Follow your team through the corridors, a drunk man appears (if you Knife the drunken man and the two sleeping Enemies in the room he came out of this unlocks the ''three of a kind'' achievement) in the room with the sleeping men is a Enemy inteligence (A Collectible in COD 4, total of 30)
3. SLIGHT DANGER
Follow your team to the other side of the ship, you dont need to shoot the two on the platform. When Price says 'we've got company' take cover because the enemy starts shooting at you with LMG's. wait for the chopper to sort it out.
4. MOST DANGEROUS
When you get inside to the corridor where you get 'ambushed' then you can leave it to the AI, but they will normally leave one alive for you to kill. When price throws a flashbang through the door, hang back, the AI will handle any enemies down there. and then follow when clear Sometimes there is an enemy with a desert eagle in a container as you go up the little staircase. He can tear you to shreds. follow the squad to the next catwalk, but stay on the catwalk to clear enemies, you can see more. At this door that you go to breach through there should be a checkpoint. when the squad goes through wait for a while and then go to the first box in front of you. no enemies can flank you from here. when you can hardly hear any gun fire move up to the right of the truck if the enemies on the left. if he is on the right then you can just stay at the box.
6. LITTLE DANGER
Some missiles are coming your way to the ship, grab the manifest. and follow your squad, when you get to the next room the ship starts sinking. to get out of there just follow your squad. go to the chopper and press A to jump on when it tells you to.