On round one buy "Quick Revive". Now shoot a zombie twice with the M1911 then knife.

After doing this the whole round you will have atleast 940 points. Now you should buy the M14.
Since it is round two, shoot the zombie once with the M14, then knife. It will only be one knife. Same thing for round three, shoot a zombie twice with the M14 then knife once and so on.

At the end of round 4 leave one or a couple zombies and open the upstairs door.

Doing my strategy you should have atleast 4500 points. Keep opening doors until you find the random box. If you don't find it when you get to the room with the power switch, turn it on.
Link the teleporter. Once you have done this go to the room with the big stare case, which is the one after the first door I told you to open.

Once you have this kill the last of the zombies. Once you kill the last one, go back to the teleporter. Stand in it and keep killing zombies until you start getting too many to handle.
When this happens teleport (hold in X). Once you're up there keep shooting zombies and throwing grenades.

Once you have teleported back stand their and keep some crawlers. When there is about three go around back to the teleporter the way you first came opening the doors.

As soon as you can link the teleporter, do so immediately. Do this until round 13. Now when you're standing on the other side of the teleporter when you teleport back, watch your back because zombies will now come behind you.

As soon as you can find the box, do so and buy it. When you get a gun you like that is good.
Once you teleport their will be something behind you called "Pack A Punch" that costs 5000. It will upgrade your gun into something even better that will pone.

That's about all. So do my strategy and you will get far.