Are you up to the challenge?
When playing Call of Duty 4 online, you gain experience points based on feats you perform in the game. On top of your regular experience gained from killing enemy soldiers, you can also get bonuses for performing some specific actions. Many of these can be attained simply by playing the game, though some require special effort. If you set out to accomplish all of these Challenges, you will rise in level much faster.
The Bootcamp Challenges are the first set of challenges that are given to you upon reaching 9th level. They come available a few at a time, until you reach 18th level. When you reach the 21st level, the Operations Challenges become available. You do not have to complete all the Bootcamp ones to progress to the Operations set. In fact, you're not required to complete any of them.
Call of Duty 4 Bootcamp Challenges:
Radar Inbound – Kill 3 enemies without dying and call in a UAV. (50 xp)
This one is pretty easy to get, plus very helpful in the game. It lets you see where the enemy soldiers are hiding.
Airstrike Inbound – Kill 5 enemies without dying and call in an Airstrike. (50 xp)
This one can be a little more difficult, but once you get the hang of the game you ought to be able to get it at least once per session. Combine this with the UAV and you can rack up all kinds of kills.
Chopper Inbound - Kill 7 enemies without dying and call in a Chopper. (50 xp)
This can get tricky because on a busy map, it is tough to get 7 kills in a row. If you can get the Airstrike option and stay alive long enough to use it in the same round, then you can get this Chopper one pretty easily.
Fly Swatter - Shoot Down a Enemy Helicopter. (250 xp)
Just as it says, you need to take down enemy choppers. Even if you don’t have a rocket launcher, a regular machine gun can still do damage to it.
Marathon - Sprint for 26 miles. (250 xp)
This one takes a while to complete, but all you have to do is run around a lot. I thought this challenge was pretty silly.
Goodbye - Fall 30 feet or more to your death. (250 xp)
All you have to do in this one is fall from a tall height. You can always find a building to jump from, or a missile silo to jump into.
Base Jump - Fall 15 feet or more and survive. (250 xp)
You’ll probably get this one the first time you jump off a ledge. You will take some damage when you hit the ground, so don’t do it if you’re already hurt.
Crouch Shot I, II, and III - Kill 5, 15, and 30 enemies while crouching. (50, 100, and 250 xp)
You can get this one just by playing the game. I pretty much stay in crouch mode while playing because it gives the enemy a smaller target.
Prone Shot I, II, and III - Kill 5, 15, and 30 enemies while you are prone. (50, 100, and 250 xp)
Again, you can get this just from playing. Just know that you can’t always move that much when prone, so check your field of view before settling into position.
Grenade Kill I, II, and III - Kill 1, 5, and 10 enemies with a grenade. (50, 150, and 250 xp)
All you have to do with this one is toss a bunch of grenades and wait for the kills to add up.
Point Guard I, II, and III - Get 5, 15, and 30 assists. (50, 150, and 250 xp)
This is one you’ll get just by playing. Since everybody is shooting at everybody else, there will always be times when two or more people fire on the same person. When this happens, assist points are assigned to all who contributed.
X-Ray Vision I, II, and III - Kill 1, 5, and 15 enemies through a wall using Deep Impact. (50, 150, and 250)
This can be a tougher one, but incredibly useful when taking out guys hiding behind walls. It works great for snipers hiding behind windows, too.
Vandalism I, II, and III - Blow up 1, 5, and 15 cars. (50, 100, and 250 xp)
In some of the maps, abandoned cars are everywhere. Sometimes there are two or three close enough to each other that you can blow them up with a single grenade. This is also useful for taking out guys trying to hide behind cars.
Backdraft I, II, and III - Destroy 1, 5, and 15 enemy explosive device. (50, 100, and 250xp)
When going into enemy territory, it’s not uncommon to find a laser tripwire mine that an enemy planted. All you have to do is shoot it.
Knife Vereran I, II, and III - Kill 1, 5, and 15 enemies with your knife. (50, 100, and 250 xp)
I love getting knife kills because it’s sort of an insult to whoever you knife. This is one you’ll eventually get just from playing the game.