To get most of the points on Call of Duty 4 requires you to play it on Veteran, which is HARD. However, there are are ways to make things a little easier including some cheats. I am not going to lie to you, it will still be a hard, but at least if you get stuck, you can try some of these cheats.

Please note that these are not coded cheats but rather tactical in-game cheating. Fooling the AI so to speak.

One Shot One Kill Cheat 

This is an easy way to beat the level One Shot, One Kill, on Veteran. In the last spot where you need defend an injured MacMillan, there is a sweet spot where the enemies do not spawn. It is behind the building on right, if your back is to the Ferris Wheel, and is shown on this YouTube video below. Drop off MacMillan, then go prone around that building. I actually never used any claymores, like in the video (but you can if you want to). I just hid around that corner and picked about only three enemies while prone. Wait until the helicopter lands, then you got about 30 seconds to run for it and pick up MacMillan. A lot, lot easier than defending around the Ferris Wheel! Credit goes to Kurozuguchi for the video.