I read this on Practical Painting and thought it was interesting... wished to share with you.
One thing I like to do, no matter what I am doing.. a painting, drawing or sketch is look at my work throughout the process via a mirror. This really gives you a different perspective. We get so used to looking at our work that we almost "stop" seeing it clearly. Using the mirror and looking at the reflection is like looking at it with a different pair of eyes. You can instantly see problem areas, perspective issues or if shadows and highlights are not correct.