Sprays are fun player-chosen pictures you can post in Team Fortress 2 (or pretty much any other source game). As it would suggest, the character “sprays” them on the wall like they’re graffiti, and to a lot of people they’re treated not much better. However sprays can have some effective (and rather sneaky) uses.
Tutorial articles
How to Create Custom Textures for the Source Engine

This tutorial will show you how to create custom textures for use in creating maps for the Source engine. The process is also the same for creating textures for models, sprays, mods and essentially any image data within any Source game.
5 Reasons You Should Bind a Key to Suicide in TF2

Dying is almost always a bad thing in Team Fortress 2 (indeed, most shooters). You aren’t helping your team while dead, you aren’t having fun while dead, and a good many unlocks are dedicated to keeping the player or his teammates alive. Trying not to die is, for the most part, a pretty good strategy and you’ll go far with it.
A Guide to Lighting in Source – Part Two

If you followed Part One of this guide, you should have some idea about the Source engine’s basic lighting capabilities. Now let’s go a step further to look at the more advanced techniques that the engine has to offer, including the extra capabilities of Portal 2, CS:GO and Dota 2.
A Guide to Lighting in Source – Part One

Thanks to our previous Source tutorials you may have created an excellent map, but without lighting your players are going to feel left in the dark.
There are a range of different entities responsible for providing illumination in the Source engine, and the number and complexity of options open to you depends on which game you are mapping for. This guide will begin with basic lighting for Half-Life 2 and other Source 2007 games, before shedding some light on more complicated techniques.
Beginners’ Guide to Triggers, Inputs and Outputs in Source

If you followed our first Source SDK tutorial, you should have gotten to grips with the basic features of Hammer: you can use brushes to create rooms and corridors, change textures and place props. Your level is still mostly lifeless though, so it’s time to use Triggers to make things happen.
Make Your Source Maps Glow with Cubemaps and HDR

Is your map looking a little bit flat? Does it need that extra zing? Then High Dynamic Range can help you add that warm glow to your creation.
HDR is a subtle effect; a simple explanation is that is the effect of your eyes adjusting to a dark room after being in the bright outside. This means that darker areas will be darker initially, and will then rise to a brightness level more suited for interior gameplay. This dynamic balance of brightness adds contrast to your map, meaning an overall brighter and vibrant experience.
Absolute Beginners’ Guide to Source Mapping

Welcome to the first of our new Modding & Development Tutorials. In this installment we’ll help you take your first steps into creating a map in Valve’s Source SDK.
Creating levels can be challenging, fun and very rewarding (albeit sometimes frustrating) and you will be able to release your creations to thousands of players worldwide.
Fixing Half-Life 2 and Portal Mods on SteamPipe: A Quick Guide

As described in our Roundup, due to SteamPipe a lot of Source mods are in a pretty dire state right now. Whilst there is a lot of information on the topic in various places, the aim of this post is to provide a general fix for Half-Life 2, Episode 2 and Portal 1 that you can use to easily patch up the majority of the casualties and get them limping back into action.
Hammer Tutorial: The Basics

Learn how to install the Source SDK correctly and how to use Valve’s Hammer Editor.