Typically, about every strategy here will get you through the rounds. Mine is a bit tweaked, but I'm more of a point muncher than I am kill hogger.
Rounds 1-5: Use your M1911 to max out your points. The first round takes 6 bullets to a zombie's chest, followed by a knife. Add around 4-6 bullets per round. Let the zombies break through the barriers (to increase chances of power drops).
Rounds 6-10: By now, you should have at least 3000 points (minimum) to work with. Head out to the Stakeout room and pick up an MP40. Personally, I like to guard the staircase (coming from the hallway), since more zombies will spawn there. Headshots are a plus, as they do +100 points. If you find yourself low on ammo, it'll only cost 500 points (at the end of Round 9, you can get up to 10,000 points flat).
Rounds 11-20: The theater room is now your battlefield. You can choose two loops - the middle-front of the stage, or the loop from the lobby all the way to the theater. Juggernog is a MUST if you plan on running from zombies. Let zombies cluster to make a rape train. If you still have your MP40 (best advised w/o PaP), headshots will score you some major points (though they are not needed, it'll be a good choice once your train becomes a mob).
Rounds x>21: You can use the loops to survive for as long as you want. If needed, PaP your MP40 (advised if you have more than 10,000 to spare). Be aware that ammo will run out soon, so form trains to your advantage. If you're running around the front stage and lose ammo, run the lobby loop to the theater and pick up some ammo along the way.
Tips:
- Although not necessary, Quick Revive will be helpful for reviving down teamates that are near you (a MUST during 20+ rounds).
- When forming a rape train, avoid sprinting to allow the slower zombies to catch up. Only sprint if you're being surrounded.
- ALWAYS have a weapon for close combat. When I'm surronded and the MP40 will not help whatsoever, I whip out a Mustang & Sally (or any PaP'ed shotgun) to make a break for it.
- Mystery Boxes are basically death traps. Only use if your secondary sucks or you run out of ammo for it and need something to blast zombies with.
- The best weapon combination to have is one off-the-wall weapon and a Mystery Box weapon. Use up your MB weapon last (that is, if it's trong enough) as your back-up. You can always grab ammo when your OTW weapon is out anyways (unlike the MB weapon).
- Even if you're beasting rounds like no other, making a crawler will give you and your team a chance to recoup to repair barriers, buy ammo, set strategic routes, etc etc.
- I found Claymore to prove extremely useful in dire needs. Plant some in front of the Juggernog corner. Why? If you are downed and suddenly get back up, you can head over to Jugg quickly without worrying about zombies taking you down. This works with any strategic spot.
- In reality, Jugg and Quick Revive are the main perks you want to get your hands on. Anything else is optional, but not advised.
- The Balcony (room above theater) is a perfect place to camp out and earn major points with grenades. After teleporting back to the lobby, toss some grenades toward the theater door. Try to stay within the lobby until there are too many zombies to handle. Break into the loop.
- If running the loop, NEVER have two people running together or even countermotion. Keep some good distance away from each other, and always flow with the traffic.
Hope this help!