(adsbygoogle = window.adsbygoogle || []).push({}); The Ally:
When you are looking at the PaP machine open the door to the left and work your way around to the inside of the other door and this is what you do...

3 people look down the ally and the other person covers the window. The window man is the most important man in this strategy. In later round there may need to be 2 covering the ally and 2 covering the window. Never open the the door to the left when you are looking down the ally!

The Balcony:
At PaP machine get to where the first box is by opening either door, it does not matter how you get there. The balcony is behind the door you have to open when you are facing the bridge it will be behind you. Open the door and climb the stars and here is what you do...

Climb the stars and 1 person covers the window and the rest can cover the stairs, the incoming zombies or whatever. Never get in the hole where the box is, that is where you will die.

The Quick Revive Room:
You get here the same way you would get to the balcony but instead of going to the stars you make a left before the room that has the steps in it and the is a Quick Revive machine. Here is what you do...

One person will stand at the window holding square and shooting either the zombies trying to break the window he is constantly repairs or shoot the zombies coming in the entrance of the room. The other 3 players will kill the zombies coming into the entrance. If you are looking at the entrance there is a hole to the right so be careful not to fall in it if you do this. If you feel you may die simply fall into the hole and do not leave, if you do fall in the hole your team mates should follow to help you hold them off until the next round.

with friends its alley for me
with random people its ALWAYS the balcony

but i dont mind either way

Dude, the best way is the balcony. Have someone kill the ones at the bottom of the stairs and when he needs to reload the other takes over, and when he needs to reload the other takes over until all the zombies are gone.