Forrest Imel is a Senior Concept Artist at Blizzard Entertainment. In addition to his full time work, he also does a lot of freelance work for companies like Wizards of the Coast, and somehow still finds time to make instructional videos on the side!

He recently released a really great video about how to render different materials. So much about painting realistically comes down to the convincing depiction of texture, which ultimately is about the varying reflective properties of different surfaces. In this video, Forrest goes over some of the most basic principles of lighting, and then shows you how to tweak that process to give the impression of different materials, all in a very simple and concise manner that makes it easy to understand.

Beginners and pros alike will find something useful here:

Forrest has quite a few tutorials available on his website going over a lot of basic art principles.

You can find more videos like this one right here: