There are also a lot of online resources that provide instruction on how to improve your art techniques. Here are a few introductions to get you started:
Ten-Minute Drawing Techniques
Narrated instructional videos for budding illustrators with short attention spans!
I love the Ten-Minute Drawing Techniques site, because I rarely have more time than that to spare, but I really am interested in improving my artistic skills. Mark Chong is a part-time Video Game Concept Art instructor at the IADT (www.iadt.ca), Freelance Illustrator, and Former Feature-Film CGVFX artist. He is also informative and entertaining.
DrawSpace.com has an amazing variety of lessons available for free to registered users. Whether you are a beginner, intermediate, or advanced artist, Brenda Hoddinott and her DrawSpace art instructors have something to help you hone your skills. Signing up is easy and painless. I was reading my first lesson within three minutes.