If you have it on Xbox 360 or PS3 just play online and keep doing online matches till you get to level 4. You get points when you kill someone or send in air strike or helicopter. Air strike is 3 kill streak and I think helicopter is 5 kill streak. If you have been leveled up in the middle of a match online It will say You've been promoted! E.g: Yo've been promoted Gunnery sergernt 1.
In Call of Duty 4: Modern Warfare, the M14 rifle is unlocked at Level 46 in multiplayer.
15+ i think
Level 38, Lt. Colonel 1
level 4
Kill the boss in the last level.
depends if you are refering to live or what
You have to get to level 4.
There is none
by killing enemies, if your talking about online
play search and destroy
get to level 55
Yes.