Lessons I've learned and that I wish someone had taught me when I was first starting out.
For all of you beginners out there: it's a challenging, frustrating, but ultimately rewarding path.
You need three things to succeed:
Passion - If you don't absolutely love this stuff, you won't stick with it. Period.
Patience - Things won't happen right away. It will take years to get anywhere. It will take longer than you think it will.
Persistence - Don't give up, no matter how frustrating things get. You will fail often; accept this and learn from it.
Lessons for beginners
Drawing on the Right Side of the Brain: http://www.amazon.com/Drawing-Right-Side-Brain-Definitive/dp/1585429201
Highly recommended for anyone just starting out, especially for those who think they can't draw.
This book teaches you how to perceive in a different way and removes a lot of roadblocks that beginners often run into.