(adsbygoogle = window.adsbygoogle || []).push({}); Okay, i know some people are probably aware of doing this but follow the steps:
1-2, maybe 3 people if you are all good.
R1:Knife (DO NOT BUY starting wall guns)
R2:Knife
R3:Knife, shoot and grenade(only 2)
R4:Shoot and grenade, buy door if in trouble and buy MPL(get anyway)
R5:Buy elevator barrier and kill, if the round is about to end make a crawler(always try to make 2) but go down if in trouble
If money is good, go to box, DO NOT TURN ON THE POWER YET.
Go upstairs and elevator camp.
R6-9: Fight as normal, elev camp and always attempt to start away from third level or you will get gas zombies attacking you no matter where you are.
(Juggernog is a must before round 9, if you dont have great guns go for and MP5 or something)
Crawlers are a must every round now, and always activate the defcons, only do 4 and leave the one closest to the elevator downstairs.
When you activate the power the theif will appear 1-2 rounds after you do so, make sure you are in the middle every round at this point and find out who he is chasing(you will be the only one who can see him unless you have been caught) and watch from the upstairs railing, all the person who he is after does is run round the upper walkway while everyone else shoots.
claymores are really handy, and also clear all the 2nd floor debree.
From here on start at the defcon switch you havent activated, when the zombies get a bit scary activate it, and go through the teleporter, if you dont go to the PaP room just go through the teleporter again, while in here PaP only when you have low ammo, the PaP sale is on, remember if the theif is going to come do not PaP your weapons. while in the room put your claymores in th door way, space them out and when the door opens throw all grenades, then make a break for it and lap the lower level, if the going gets rough you may need to buy the stakeout, this isnt ggreat but if your good, you will survive with it. Repeat this and you should get to atleast round 18, me and my freind got to round 26 before getting stuck on the pesky objects and had the crap slapped out of us so you need to:bro: and dont :catfight:
ENJOY!

I do this, though. In any case, I confirm the general strategy works. I got to round 34 with good team-mates I know irl [aka good teamwork]. Though I strongly suggest to make your own strategies based off of this one. Who knows, you could get much farther then we ever did. :]