Camping is easy if played right. I played at my friends house, after a GTA V session he persuaded me to have another go on Black ops 2, so I said ok let me play like a mofo and camp my ass off. It was a real bad camping class but I just didn't care I was playing for a laugh.
Anyway it was the express map and I set up an Assault Shield to the left of where the train comes out of the tunnel as you face the direction of where the train is going. Couple of shock charges were thrown out for warnings and just sat behind the shield with an MK 48 no target finder and just using iron sights. Also had some EMP Grenades. It wasn't great but I went 9-1.
Imagine if I had have gone full hog and used Shock Charges with Claymores or Sweaty Bettys, Scavenger. Flak Jacket, and Tac Mask.
Used the target Finder on the MK48.
I probably could have done a lot better than I did and I don't play this much maybe once every 2-3 months. So if you live on this damn game you can learn to camp and make people rage quite easily.