its simple for me.
rounds 1-4 stay in first room if ur bad with the sniper on the dogs
but sometimes ill stay until 6-7.
after that open the door upstairs and hold off against next wave or so, if u get backed
up go through the next door to the room with speed cola (make sure u save at least 2500 points before leaving this room).
hold off there for about 3/4 of the round with the mp40 and go through door at bottom and once again
mow a few down and go through the door into the theater so here you could be at round
8-11 then (i hate this room, too many corners with the movie board) i usually hold off 1/3 of the round then flip the power on and MOST IMPORTANT-get juggernog then just stay in the theatre at the beginning of each round and go around the circle getting zombies to follow you and every 2 rooms or so stop turn around and kill some and repeat this each round. gets me to rounds 150-250 :D