the best strategy in the game is the following; the more players better though, if they play well and dont jerk off everywhere
you stay in the first room for at least 5 rounds using 4-8 bullets on every zombie depending the level, just to wound them, then knife, and i get out of the first room with like 5000 already..
then go all the way round in the alley and dont open that last door infront of the double tap machine
onecan get the window, probably the one with the worst guns, and the other 1-2-3 stay close to the brickwall besides the stairs and if you have rpk or hk which i love, you can get so many headshots if youre good at aiming, they all come at the same place though
keep getting a crawler at the end of rounds unless you got max ammo in that round.. and upgrade and get better guns and try for the monkey bomb, if you got a thundergun and the monkey bombs, damn use the thunder when they all around the bomb its mental.. ;)