Four survivors, hundreds of zombies, one escape vehicle: the concept is simple, but staying alive is not. Make things easier on yourself and discover some of the game’s secrets with these handy tips.

(1) Sounds of the South

Jukeboxes play random tracks, including (very rarely) Portal hit “Still Alive” and (more often) “Re: Your Brains,” a zombie track by the same composer, Jonathan Coulton. If you stay and listen, the chorus always triggers a zombie horde. Prep yourself by listening to it on his site: jonathancoulton.com/store/downloads.

(2) Get Gobby

The Spitter is like the Smoker: not much good closeup but lethal at long range. In Versus, use her carefully to block doorways and exits so the Survivors can’t get past. For best results, do it as they go through, separating stragglers from the group for other Infected to snack on.

(3) Protected Parking

When you climb out of the sewer in The Parish, switch to melee weapons until you’re through all the parked cars in the impound lot. Using guns will likely set off one of the alarms, and it’s easy to be overwhelmed.

(4) The Strongest One There Is

Several of the attractions in Dark Carnival still work, and if you aren’t being flailed to death, you can get Achievements for beating them. Most are straightforward, but you’ll need a shot of adrenaline to hit the bell on the test-your-strength machine — and to deal with what follows, too.

(5) Easy Rider

If a teammate has been pounced by the Jockey, don’t worry too much about shooting them. Your fire will be soaked up by the Jockey and the player will remain largely unhurt while he’s in place, so you can break out the grenade launcher with a clear conscience.

(6) Gnome and Away

Half-Life 2’s gnome reappears here as a prize in the shooting range in Dark Carnival: win him and carry him to the end to unlock an Achievement and an Avatar award. You don’t have to carry him every step, though: the level is a maze, so look for fences you can throw him over and pick him up when you reach the other side.

(7) Trigger Happy

Over the course of Hard Rain, you work your way from boat to gas station, then back again. Items don’t respawn for the return journey: ration your health packs carefully so you have some for the way back.

(8) It's A Sign

Keep an eye on the mobile road signs scattered throughout the level. They’ll often advise you on where to go, but other times they’ll display random messages. They’re one of the variables Valve has added to make each playthrough slightly different.

(9) Uncommon People

Each campaign has unique zombies. Dark Carnival’s clown attracts other zombies with his squeaking feet; The Parish’s SWAT needs to be pushed away and shot in the back; Hard Rain’s builder can’t hear pipe-bombs; Swamp Fever’s mudman crawls under water and spits in your face. Attack accordingly.

(10) Ready to Drop

In Swamp Fever, always check out the dead parachutist hanging from the tree. It’s one of the weapon spawn points, so the Director might have left something useful. It’s particularly helpful in Realism mode, as you can see it from a distance rather than having to ferret around in dark corners of uncertain safety.