Just kill people
you have to get kills on your friends or on wifi the more kills the more guns
You have to be online, and the only way to unlock guns is to level up. Just keep leveling up and you will start unlocking guns, perks and new challenges.
That depends, if you prestige then you are simply doing the multiplayer part of the game over again, and since your doing it over again you already have some experience, and therefor it maybe easier to unlock weapons again.
you have to rank up to earn game modes, weapons, perks, and equipment
you unlock it by doing multiplayer it just matters how much kills, or falling, and random things you do
On Modern Warfare 2, you earn weapons for multiplayer by achieving higher ranks in multiplayer.
you have to get kills on your friends or on wifi the more kills the more guns
You need to get to rank 50.The only way to unlock the Javelin is by playing the Multiplayer on Modern Warfare 2, just like to do with every other gun. It is unlocked at level 50, and when you prestige, you will have to reach level 50 again to unlock it, like the other guns.
Just play the game. It is unlocked at a very low level in multiplayer. It shouldn't take long to unlock it. Maybe 1-3 games.The Walther P99 handgun is unlocked at Level 10 in the Multiplayer mode of Call of Duty: Modern Warfare 3. In Survival mode, it is unlocked at Level 42 and costs $250.
In Call of Duty 4: Modern Warfare, the M14 rifle is unlocked at Level 46 in multiplayer.
When you reach level 38 you wil unlock the Overkill perk. You can use thi perk as your second perk and it allows you to use two primary weapons
-aw3somef1rep0wer will unlock the USAS12 Shotgun in multiplayer. That's the only cheat to unlock weapons (that I know of).