Get some perspective...

Any good sketch or drawing, particularly visualization of space, relies on the artist having a solid understanding of perspective.

Working with 3D applications like Sketchup or 3DS Max eliminates the need to manually walk through the steps of setting up accurate perspective every time, but this should never be an excuse for any 3D artist to lack the fundamental skills of basic and even some advanced perspective.

I highly recommend the three-volume series Fundamentals of Perspective by Gary Meyer, available from The Gnomon Workshop.

  

In this series, Gary Meyer walks you through the step-by-step process of creating accurate one, two, and three-point perspective. All of these approaches are crucial to creating concept art, as well as other types of illustration.

Professionally mastered tutorial videos tend to be a little pricey, especially for young artists, but if you're serious about learning to draw or (like me) improving the skills you already have, these are worth the investment.

Another good resource is the book Vanishing Point: Perspective for Comics From the Ground Up by Jason Cheeseman-Meyer. Although geared toward comic art, this book covers more advanced four and five-point curvilinear perspective. It is available from Amazon in both print and digital editions.

And no, I don't get kickbacks from either Amazon or The Gnomon Workshop for promoting these two resources. They're both just great places to start if you need a tighter grasp of perspective.

-DLA