Suppresive Fire

So you and your teammates are taking heavy casualties from a enemy camping in a window in the back of the level. Every time you try to take him out he gets you first, because he has a superior cover and a height advantage. A technique you can use to get close enough to take him out, is to lay down some suppressive fire. This works best when you have teammates helping, but you can also do it alone. It also works best when you are using an Light machine gun class, because they have lots of ammo.
what you want to do is take cover as close as you can safely get with a view of the window. When you see that stinking campers head pop up, start firing. The effects of suppressive fire are psychological, so you want him to fear for his life, and take cover. Once he has taken cover, you can advance to the next nearest safe spot and repeat. You wont have much time so you have to move fast. You can see how having teammates would help greatly. Your team can help each other leapfrog from position to position. If you lucky he might not see you move, and think there are more of you than there actually are. Once you are in a close position, take him out with a frag, rocket launcher, grenade launcher, shot to the head, or whatever gets the job done. Be sure to watch the exits from that building in case he tries to make a break for it. also beware of tactical insertions, so you don't get killed again immediately.