Left4DoD is a  horror WW2 game based on the VALVe game Day of Defeat: Source
It is a game for up to 14 US players and 4-8 Zombie players. 

Most of the Zombies are Axis bots. They will try to cap the flags. 
If there are more than 7 human players, then spots on the Zombie team become available for human players to play as Special Infected.

The Zombies generally run from spawn, but they can also be picked up by one of the Special Infected and teleported near you. The Witch can move anywhere on the map, so keep your wits about you.

So Left4DoD is pretty simple to play...

  1. Kill Zombies
  2. Survive if you can
  3. Capture the flags

PLAYING AS AN ALLIED PLAYER

How do I get health when I'm injured?
Pick up the red first aid box left by a Zombie when it dies.  If you already have health, you will get a healthkit which you can throw down and use later (say !drophealth to drop a health kit). Sometimes, you might have hardly any health, and you can't leave your spot, so you can have a team mate to drop you health (with !drophealth)
Sometimes, a Zombie will drop pills.  Pick this up and you will get a major uber health boost!

If you have collected enough money, you can buy health or armour from the Store. Money comes from picking up helmets that the Zombies drop. The are either $1, $10 or $50 helmets.

How do I get more ammo?
Pick up the green ammo box left by a Zombie or Allied player when they die or ask a team mate to throw you an ammo box (press H)

What is the little Green phial of stuff?
That is Zombie blood - if you take it, you will disappear and the Zombies will be unable to see you.
You will also be invulnerable for a short period of time.
Oh and you can see through walls to find all the Zombies near you!

What is a Bottle of Hooch?
An alcoholic drink, when taken gives you a speed upgrade with no loss of stamina, meaning you can sprint all over the place.  But then comes the hangover...

What is a Box of Nades?
Um...it's a lot of grenades - 5 to be precise or 10 if you are a Left4DoD Supporter.
Have fun nade spamming!

If you have collected enough money, you can buy a Box of Nades from the Store.

What is AntiGas?
The Gasman's red gas will hurt you a bit, so finding this will help and counteracts the effects of the gas! It lasts for 15 seconds.

What is TNT?
In Left4DoD, you can plant TNT anywhere. On any surface.
Just hold down the USE key, (usually E) and the game will create a little yellow TNT holder where you can plant TNT.
Once planted, the TNT will burn for a second then it will turn red...this means it is primed and can be shot at, to detonate. Stand well back, as this beast packs a punch.
You can also throw the TNT on the ground and shoot it from a distance or just let the Zombies run over it.

What is an Airstrike?
If you pick up one of the large radios, you can call in an Airstrike in a designated area.
Simply press the USE key (usually E) while pointing your crosshairs where you want the bombs to land.

If you have collected enough money, you can buy a radio from the Store.

  What is the Shield?
The Shield is a device that blocks Zombies getting close to you. It lasts for 15 seconds and throws up a ring of bars that will destroy any Zombie running at you. Handy for blocking those caps! Simply press the USE key (usually E) and the ring of green bars will appear around you.

How do you use the Flamethrower?
Point it at the Infected and press E or whatever your +USE key is

If you have collected enough money, you can buy a flamethrower from the store and flamethrower fuel, too

What is the Red Gas?
Don't go near it.  It's the GasMan's way of killing you.  It's a Gas Bomb. He can shoot you from quite far away.

Why did I just blow up, spontaneously?
Ah.  That might have been The Emo. 
He is a terminally depressed guy who looks a little bit like Hitler. 
If he gets near you, he'll explode.  So....guy dressed in black = run away.....
Shoot him in the head because it will reduce the effect of his explosion

WTF? Zombies suddenly spawned beside me or in me???
The Grey Dude is nearby.
His ability is to be able to spawn two zombies where he wants.
They can appear in a cloud of smoke beside you or even behind you...

You'll see a big red line appear and bright light where he has teleported Zombies.
Use this to track where he is hiding.

Are some of the Zombies bots?
Yup.  They cheat, hack and teleport!
They also aimbot with the spade which means if they get close to you, it can often be a one hit kill for them.
Some of them are human.  They are wily, cunning folk who enjoy sneaking up behind you, so work as a team and watch your back.

How do I get German weapons?
Use the menu at spawn or if you accidentally hide it, type !menu to get the extra weapons.

Have you any general tips for playing Allies?

 

PLAYING AS A ZOMBIE

The Zombies

How do I play as the Witch?
She is fast and frail.  She can accelerate away quickly and can also teleport.  Point your cross hairs where you want to teleport and right click (or +ATTACK2).  Just keep moving and the US soldiers will have a hard time hitting you. Pressing +JUMP (space key) several times will make her triple jump through the air.

The Witch is excellent for getting rid of those pesky snipers or machine gunners.

How do I play as the Infected One?
He is capable of disappearing.  Right click (or +ATTACK2) will make you disappear in a cloud of smoke.
To play the Infected One properly, you need to go behind the lines and use your Allied uniform to fool the US soldiers and stab them from behind.  Beware of flashlights when invisible...your shadow will be visible!  

Quick tip - if you see Allied soldiers, turn your face away because that will give you away.
Some players cleverly use their flashlight to add to the disguise. But Allied players quickly clue in as to who you are since a name does not pop up under their crosshairs. So keep moving.

How do I play as the Gas Man?
Right click (or +ATTACK2) and he will release his gas. He can fire Gas Bombs into places the Exploding Skulls can't reach, so use him to get rid of those snipers/campers.

How do I play as the Grey Dude?
If you right click (or +ATTACK2), and point your crosshairs ahead of you, one or two zombies will be summoned to that spot.  Sometimes one of the summoned Zombies will be an Emo....hehe. A great way, when many Allied players are ganging up on you, is to summon a couple of Zombies behind them and let them confuse the enemy giving you a chance to get away!

It's important to understand that the Grey Dude is the team controller. He can block flags being capped by summoning two Zombies on or near the flag, he can provide a shield with bots or he can cap 2-man cap flags with his bots.

How do I play as the Anarchist?
If you right click (or +ATTACK2), you can lob skulls in front of or behind the Allied players, where they will explode. They are difficult to control at first, but you'll get the hang of it!

Learn how the skulls bounce. You need to learn to bounce them off walls and objects.

How do I play as The Emo?
You can become an Emo by buying the class at the Store. If you have collected enough helmets, you should be able to purchase the Emo.
Right click (or +ATTACK2) will make the Emo detonate.  Try to get as close to as many Allies as possible.  Sneaking around in dark places is also a smart idea as his dark clothing will hide him well.

Use the ESP and find as many Allies as possible.

The Emo is noisy. He begins screaming as soon as any Allies are nearby. However this can confuse them!

How do I play as The UNG?
You can become an UNG by buying the class at the Store. If you have collected enough helmets, you should be able to purchase the UNG.
The UNG has no special abilities except that he has lots of health. But he is slow...very slow.
Choose a target and stick with it!

How do I play as The Wraith?
The Wraith is the team medic. He can suck health/life from Allied players. Right clicking (or +ATTACK2) will activate his 'Suck' which will suck the health out of Allied players.
He is also the team doctor, so a Wraith can heal team members. Use right click to heal. The beam will be a different colour.

How do I play as the Skeleton?
You can become a Skeleton by buying the class at the Store. If you have collected enough helmets, you should be able to purchase the Skeleton.
The Skeleton can jump all over the place. It has a triple jump meaning you can run in stabbing and then run away! He is armed with several nades that are detonated remotely. Switch to grenades, lob them then back away and RIGHT CLICK to detonate them.

Why can I see through walls? Will I get VAC banned?
No. You won't get banned.
This is a server side modification so that the Zombies can see the Allies better. Allied players will show up as lines. The bigger the line, the closer they are.
Allied players that are low in health will have orange/red lines so use that to your advantage.

Have you any general tips for playing Zombie?

 

GENERAL STUFF

What is the Store and where do I get money?
Every time you pick up helmets or capture flags, you get money.
Collect enough money and you can purchase stuff at the store such as special weapons.
To get the store type in chat: !buy

I was kicked?
In order to play Left4DoD, I require you to have  cl_downloadfilter to 'all'.
These are not admin sounds, or dumb songs or anything useless like that.  They are Zombie sounds, Zombie models, Medic boxes and other stuff that makes L4DoD what it is.
You will find this in Options > Multiplayers.

Why do I see giant Error signs running around?
You didn't download any of the models. Set cl_downloads to '1'.
You can't play the game without the models. So exit and re-join.
If you are still finding it hard to get the models and materials to download on to your machine, you can grab them from here: http://www.boff.ca/dogblog/files/l4dod.zip

Why was I banned for teamkilling?
Teamkilling ruins the enjoyment of other players. Sometimes it is accidental. If someone teamkills you and you believe it is an accident, please forgive them on the menu. It is remarkably hard to get banned for teamkilling. Five people have to refuse to forgive you in a 30 minute period.
If you have been banned, it is permanent.
Contact our Helpdesk for further information or assistance.
You may also look in our Bans List for information.

Why don't you just make it easier so I can just kill bots and get my achievements?
Do this:

  1. Install DODS SRCDS
  2. Go sv_cheats 1 followed by bot followed by sv_cheats 0
  3. Start up your new server and join it.
  4. Then shoot the bot to your heart's content

Can I get this Mod to add to my Clan's server?
Nope.  Sorry.  Left4DoD was developed for TheVille.Org. 
I would have released it if other server ops hadn't screwed up TF2 Companion Cube Soccer on me.

Can I suggest some changes?
Sure.  Register at TheVille.Org, find the forum on Left4DoD and make a comment.  If they are reasonable ideas, they might even be adopted. They often are as our players know the game pretty well!