Levels 1 – 4
As soon as the game starts, without buying any of the weapons on the wall, you should run to the each of the four barriers regularly without stopping. If you encounter a zombie, fire around three to five bullets underneath its chest then use your knife to kill it with a single hit. This will bring you around 30 to 50 points if done correctly for each zombie and another additional 130 points for the kill. In total, you should get around 160 to 180 points (Possibly 200 if you are lucky) for each zombie on the first round. As the round ends, seal up all the barriers and get ready for the next round. As the round starts, you should get a bottle of Quick Revive to ensure your survival if you do fall down. Repeat the steps from round 1, with the ‘bullets and knife’ technique to get extra amounts of points. Be aware that as the game progresses, zombies have higher health and can take more damage from your guns and knives; therefore, you should always try to weaken them while they are still breaking down the barriers to avoid getting cornered by a mob. Remember to use your knife to deliver the final blow to a zombie and not use any grenades until absolutely necessary to achieve the maximum amount of points.
Levels 5 – 10
As round 5 starts you should quickly try to seal up any barriers that are broken and open the door on the top floor to your right. By now you should have around 4000 – 5000 points if you followed the method. If you do not have Quick Revive with you, get another one, run upstairs and open the door to your right. Hellhounds usually appear at round 5 so you should do these things quickly and run as fast as you can. If hellhounds do spawn, keep on running and open all doors you encounter until you reach the stage. Over here, you should quickly turn on the electricity and link the teleporter to the pad and vice versa as you run towards and reach the lobby. By now, you should have a couple of hellhounds chasing you and a few amount of points. You should keep on running through the route you had just opened while turning backwards every so often and firing a few rounds into them with your starting gun or using your knife to hit them. Keep on doing this until you have 3000 points to buy the bowie knife, which is next to the Juggernog machine. Once you have this, use it to clear out the remaining hellhounds with one-hit kills until the round ends. Keep on using the knife and get enough to get Juggernog. Once you have this combination, just keep using the knife until the end of round 10 to rake up as many points as you can. If you encounter zombies instead of hellhounds, simply follow the same process listed above and just substitute zombies for hellhounds wherever you can.
Levels 11 – 20+
As soon as round 11 starts, the bowie knife becomes pretty useless as zombies now require a two-hit kill unless you have the upgraded ballistic knife, which provides you with a one-hit kill on zombies until round 15. Since the power is on, you could locate the Mystery Box and try getting pretty decent weapons such as the ray gun, thundergun, light machine guns, ballistic knife and monkey bombs. These will aid you in future rounds. Try getting enough points to Pack-A-Punch a weapon so its damage increases. Try running around the map and avoiding zombie hordes. Try not to get crowded in tight areas. One method that has been proven to work against zombies, is to not open the door next to the power switch, which leads to the alley. If the mystery box is in the near or in the alley, use your points to open a route to it. Use the teleporter to make a quick getaway from huge crowds. Repeat the process as long as you can.
That is the end of the guide and I hoped you benefit from it. Good luck killing those zombies!