Go to the survival map Bus Depot, stock up on weapons of your choice, but look for a pipe bomb, or (preferably) a bile bomb. Look for a line of toilet stalls on the side of the depot, there should be a newspaper box to the left of them.

Start the round, throw the bomb in front of the stalls (do not kill the infected that gather), jump on top of the newspaper vendor, onto the zombies heads, jump again onto the stalls, jump over the wire fencing on the right of the stalls, then run for the safe room.

Close the door and wait for the bots to die, then it will load the map Graveyard. You have to be quick and it may take a few tries.

To start the round, shoot a car alarm, but every time a car is set off, the round resets. Have fun.