Blind-contours - this is the ultimate building block for all other techniques that follow. Drawing your subjects without looking is the key to eliminating habits that are controlled by the logical side of the brain.
Semi-blind contours - similar to blind-contours but you are allowed the occasional look to check your work. Another great tool to connect to your subjects.
Negative space drawing - this is where you draw your subjects only using the space around them. It has a similar feel to contour drawing but different because you are focused on the space outside the subject.
Opposite-hand drawing - Have you ever tried drawing with the opposite hand? What a learning experience this is! It allows the brain to stop focusing on pre-existing ideas and techniques because you have to re-teach yourself to draw.
Upside-down drawing - an effective exercise that will shut out all previous expectations and experiences because you are seeing subjects in a new perspective. Lots of fun!
Straight line drawing - this is where you drawing your subjects without any curved lines. All curves are expressed with a series of straight lines. This is a great way to change-up your routine and add a twist to your drawing skills.