Call of Duty 4: Modern Warfare/One Shot, One Kill

This is a fairly easy mission. When it starts you will be in a hotel watching over a meeting between Imran Zhakaev and some Ultranationalist. When the wind picks up, Cpt. Macmillan says you can either compensate for it, or wait for it to die down. Be patient, wait for the wind to die down before you take the shot. When Cpt. Macmillan says shoot, SHOOT! Once you take the shot and take down Imran, a chopper tries to find you. Shoot either enemy inside the chopper and it will go down. Rappel down the window, and run onto the street. Don't get too enveloped in the firefight, move through the street and only take out enemies that are in your way. Enter the apartment with the open door, and when the dog jumps on the fence, shoot it, or else it will circle around and attack you. Plant a Claymore by the door, and shoot the enemies outside. Another helicopter attacks, but is shot down by Cpt. Macmillan, but he is wounded in the process. You'll have to carry him through the rest of the mission. Be sure to put him down in a spot where he can cover you if you get into a firefight, and make sure all enemies are gone before you pick him up again. Go through another apartment and clear all the rooms before moving on.

Waiting for the helicopter
Move through the changing room, and you will come out into a large swimming pool. Note the dogs at the bottom of the pool: DO NOT SHOOT THEM. When you come to the Ferris Wheel, first put Captain Macmillan down somewhere except for the marked area and plant all of your claymores and C4s. When you have finished, pick up Captain Macmillan and place him in the area specified and you will get more C4s and claymores to plant. Find a suitable sniping position yourself, and hold out until the chopper arrives.

Expert
This mission is probably second hardest in expert difficulty but there is a way to make the end of this mission a lot less challenging. The first thing to know is that there are two spawn-points for enemies. The first is a door behind the swimming pool, the second is another door on another road to the right of the road leading to the first spawn-point. After you have placed the claymores, head the the spawn-point to the right and pick up a second sniper rifle. Go to the end of the road and go prone, and you will see a huge force of enemies charging. You can snipe most of them as they go to attack Macmillan from the other spawn-point. As you are near the second spawn-point no enemies will spawn behind you. After the enemy helicopters arrive, you will have a much harder time with the enemies as there will be a few dogs and if you are not in the right place, people will shoot you from behind. The best place to be is in the middle of the path (so you can see well), facing the first spawn point. Move forward so you are hidden by the building so nobody can get you from behind. At the start, there will be a few enemies attacking you. Shoot them and pick off the rest as they go for Macmillan's area. Try and shoot the dogs as they come or else you will have trouble knifing them in the small window of time and when you get back, you will be standing. After you have taken care of the dogs, there may be a few others shooting at you but there will not be much to worry about apart from a few enemies that backtrack to get you. They shoot around the left corner of the building and as the spawn point is at the right, they may catch you off guard. After those enemies, just snipe everyone until the helicopter comes, wait a bit, then you have 30 seconds to get Macmillan to safety. This should be ample time and if you head to him before the timer starts, it can be even easier. You should not encounter many enemies at all and even if you just run through you should be fine.