Pick a spot. it can have multiple choke points or just the one. for this example we will use a house. run in the house, clear the downstairs. run upstairs, clear it as well. check the outsides, check behind you, run back downstairs. if you use claymores, use them here. just keep running around that house ( as long as its a relatively populated area with a good amount of activity) and repeat. you can get a lot of kills camping one "big" spot and then after a while, moving on to another.
it takes a little while to get good at it but its very much worth it if you ask me.