If you want to get to the survival achivement you have to do 3 simple things.

1.) Start Survival Singelplayer and choose weapon MAC10 (faster running) or STEAMHAMMER (slower but more powerfull).

2.) Start a server with the survial and play online with only one friend (Alone and with 2 or 3 friends is more difficult). Chosse the SCOUT. He is the fastest from all of them.

3.) Run from corner to corner along the outside. Shoot only the zombies which are coming form the outside. Leave the rest running after you.

P.S.: Look out from the beginning that your health doesn't drop under 100 in the first 5 minutes. After that you only have to live.