Camping is a generic term for multiplayer where one or more players are fixed in a position, waiting for others to enter their area to take advantage over them, esp. sniping others around the map who are not in their area per se but. Although this strategy is effective under most circunstances, camping is highly frowned on by most players online and on the console version.
Camping is most effective when there is a highly-desirable item in the camping location. Camping body armor is a common strategy and has contributed enormously to the creation of no body armor codes. Commonly, an exceptionally good weapon placement is in the room, such as the golden gun, AR33, etc.
Most campers make a point of choosing rooms that have only one entrance, and the item in that room will make it well-nigh impossible to enter. For instance, they will choose a room with only one entrance and exit while selecting a weapon able to pierce doors covering that entrance. It will be difficult for a player to enter without being slightly wounded. Similarly, a high-powered but somewhat inaccurate or close-range weapon becomes incredibly deadly when the only entrance is small and narrow. Shotguns and knives are excellent weapon choices during this situation.
The best defense against a camper is to exploit their inhibition to move out of the campsite. If you are ahead in points and playing a timed match, you effectively have won. If other players are in the stage, ignore the camper.
Explosives are a camper's bane. They can be banked around corners, and due to a thankful glitch, can also damage players through walls.
To assault campers holed-up in rooms, it is important to first open the door quickly, either from the side where it is difficult to be hit with piercing rounds, or while strafing down the corridor to take advantage of the diagonal movement glitch. Once open, quickly enter and do as much damage as possible. If the room contains body armor, collect it before attacking to ensure the player can't immediately nullify the damage received. If a door has a window it can be shot through, but this is not usually a very effective strategy. Often the player's limbs will hang through the door and can be shot more easily than you can line up a shot to hit them. However, the same exploit can be used to hit players camped behind doors or walls.
Certain weapons have natural disadvantages that can be exploited in close-quarters. Some weapons, such as the assault rifle, are so long players can't be hit by it if they are too close. Hunting knives can not hit a player that is too short or squatting down in most cases. The magnum is powerful but slow-firing, so use a faster-firing weapon and time your movement to avoid the shots.
You do not need to kill a camper in one assault. Often times, damaging them with fast, automatic fire and leaving quickly is enough to force the player to abandon the campground, often in search of body armor. You can also run a player out of ammunition by coaxing them to fire at you.