Games:

Half-Life 2
Left 4 Dead 2

Tools:

GCFScape - Extract .vpk file
BSPSource - Decompile .bsp map to .vmf file
VTFEdit - Edit loading image and chapter image

Left 4 Dead 2 Authoring Tools - Edit .vmf file using Hammer.


Basic Tutorial:

Left 4 Dead 2 Level Creation
https://developer.valvesoftware.com/wiki/Left_4_Dead_2_Level_Creation

Bot Navigation Tutorial:

Tutorial 1: Manually Spawning Zombies In L4D2 Hammer
https://www.youtube.com/watch?v=YJ1FySCixiE

Tutorial 2: Basic Navigation Mesh Tutorial in L4D2 Hammer
https://www.youtube.com/watch?v=igF1K7YA2JY

Tutorial 2.1: Drawing Custom Navigation Squares and Marks in L4D2 Hammer
https://www.youtube.com/watch?v=EAOPLxJw500

List of L4D Series Nav Mesh Attributes
https://developer.valvesoftware.com/wiki/List_of_L4D_Series_Nav_Mesh_Attributes

Finale Tutorial:

L4D Level Design/Finale Events
https://developer.valvesoftware.com/wiki/L4D_Level_Design/Finale_Events_Part_1
https://developer.valvesoftware.com/wiki/L4D_Level_Design/Finale_Events_Part_2
https://developer.valvesoftware.com/wiki/L4D_Level_Design/Finale_Events_Part_3

L4D Mapping Notes
https://developer.valvesoftware.com/wiki/L4D_Mapping_Notes

ForceFinaleStart
https://developer.valvesoftware.com/wiki/Trigger_finale

Packing Tutorial:

L4D2 Campaign Add-on Tutorial
https://developer.valvesoftware.com/wiki/L4D2_Campaign_Add-on_Tutorial

Steps:

1.Install games and tools.

2.Extract hl2_misc_dir.vpk,hl2_sound_misc_dir.vpk,hl2_textures_dir.vpk to Left 4 Dead 2 left4dead2 folder.

3.Decompile d1_town_01,d1_town_02,d1_town_03,d1_town_04,d1_town_05 maps to left4dead2 => maps folder .

4.Use Hammer editor Map => Enitity Report feature to delete useless enitity.

5.Edit maps including safe room,supply box,zombie spawn etc.

6.Generate .nav file and edit in game.

7.Test maps and build cubemaps.

8.Build .vpk file and upload.