Hey! Welcome to Easy Steps : Play singleplayer alone. (Lone Wolf)
I will show you how to play singleplayer alone. WITHOUT CHEATS, so you can still gain achievements.

First off, Turn on console,
You can turn console on by going to > options > keyboard > developer console > enabled.
or, alternatively > go to steam > library > left 4 dead 2 > properties > set launch settings > type "-console"
this will allow you to turn on console.

Second, Choose campaign,
Simple, play any campaign.

Third, Open console and type this commands,
This is pretty easy, you just type

kick (survivor name)

Dont kick yourself! (i havent tried)

Fourth, enjoy
Thank you please rate and favorite if you find this guide helpful,

Tips and Recommendations!
1) Always on the move, keep moving dont stop! (okay sometimes you can stop, i stop sometimes as well)
2) Start from easy, then make your way to expert!
3) Check my No Special Infected guide for better experience!
4) Use the CS:S Weapon Unlocker
> Find a MP5,
> Conserve ammo by burst firing
Why? Because
> MP5 has around 500 or 600 reserve ammo,
> Slow fire rate,
> Higher damage than the other SMGs
5) Grab a melee
Why? Because
> Having to reload while getting swarmed is pain in the ass,
> Can kill multiple zombies in one swing,
> No reload,
> No ammo,
> Sometimes one hit kill,
6) Use everything you find,
7) Conserve everything you find,
8) Pray to god ( if you are not atheist)