Drawing Guides
Over the years, I have come to see drawing from memory exercises as the Swiss army knives of drawing exercises. You can practice almost anything this way! 
Below are some short guides, explainers for the methods of practice I use. Also check out my weekly sessions for drawing practice. And don't forget to subscribe if you want to receive these weekly sessions in your mailbox!
Dexterity Warm-Up Drawing Exercises That Improve Pen Control And Which You Can Easily Do Without Reference
These are the various exercises I have found useful over the years for warming up and improving my dexterity in the process.
Below, I will describe some drawing warm-up exercises I collected over the years.
Doing Form Studies So That You Can Rotate Objects And Figures In Three Dimensions
Form studies help you train to place things in arbitrary orientations in three-dimensional spaces.
Form studies practice drawing primitive forms like boxes, spheres, cylinders, and cones in any orientation. These forms can then also be deformed, squeezed, and stretched. And they can be combined into more complex forms, blended, or interlocked. All this can be done without any photo reference! It is fun trying to construct, for example, imaginary cartoon characters from primitive forms.
A Primer On Drawing From Memory Exercises
I found the drawing from memory exercises really are the Swiss army knife of drawing exercises. Read more about it in this short explainer.
If you are still on the fence about doing drawing from memory exercises, then consider that this training makes you better in general at seeing what is wrong with your art!
A Fun Drawing Exercise That Will Jog Your Creativity!
Fun activities that exercise your creativity.
For some reason, we become more creative when we limit ourselves. This exercise is a great example of that: instead of having a white paper in front of you to draw anything you want, and not being able to come up with anything, you can force yourself to turn some shape into a drawing of a real person, pose, face, head, vehicle, space ship, et cetera.
Various Habit-Related Tips That Will Help You Make Time And Space In Your Life For A Creative Habit
Some tips to help you get started and keep drawing.
Designate a workspace where you will always draw and only draw. You want your mind to associate that space with drawing; you want the act of entering that space to trigger your brain to start drawing.