To survive left 4 dead 1 and 2 just follow these rules.(Warning:Results may vary)

1. Always ALWAYS avoid the witch. (Or if she's blocking your way there's a Youtube video saying to kill one use a shotgun.

2. NEVER use a Molotov on the witch cause you'll startle her and then she'll incapacitate you and she's more deadly cause she's on fire. wahmbulance

3. Throw a Molotov on Tank cause the Tank can never extinguish the fire. He'll die eventually.

4. When there's a horde, best use a pipe bomb cause the horde will follow the bomb so you won't suffer their claws and the pipe bomb can kill em in one blow.

5. Best have one gun and one melee weapon.
Preferably
Gun: AK-47
Melee weapon: Anything that suits your fancy

6. To get the 'Stronger than Mustachio' trophy. Go to the dark carnival go to the place. Use a MELEE weapon. Then inject yourself with Adrenalin. Then whack the annoying thing. (Warning: After you hit it it'll summon the horde)

7. Zombies in Hazard suits have boomer's bile, Zombies in bullet-proof armor should be hit by a melee weapon or shot at the back. Mud men will block your vision and clowns (Most annoying) will summon the horde.

I'll put in more once I get some ideas... So that's all for now... ninja