While you are drawing, how do you hold the pencil? Does your hand start to hurt after a few minutes of drawing? Are the muscles in your hand tense and taught? Then, maybe it's time to stop and shake out that drawing hand of yours. That's right, loosen up that grip and shake all of that stress away from your hand. It will be a constant balance between keeping your hand loose and maintaining a firm grip. Before you begin a drawing, I suggest taking a few minutes to stretch out your hands and arms. Doing so makes you aware of the muscles and tendons involved in the act of drawing. It is a way of connecting your mind to your body.
When you begin a sketch or drawing, keep the drawing loose. Draw with your arm and not with your hand. Use the movements of your arm to begin your drawing. Drawing with the movements of your hand is great when you are working on the finishing details, but at the start it can quickly tighten up the muscles in your hand. So remember to keep your grip loose, but firm while drawing with your arm. If it's possible, then get as much of your body involved in the act of drawing. While I was in class, I remember how I would get so involved in my drawing that it almost looked like I was dancing. Of course, this technique works best when you are completing a larger drawing. The smaller the drawing, the less movement you are going to need. Just remember to keep the drawing as loose as possible.
Drawings that were started loosely, look more dynamic and fluid. When we tighten up, we lose the subtle nuances of line weight and stroke variance. Don't forget to keep a firm grip while you are drawing. If your grip is too loose, then you might drop your pencil all of the time. If you tighten up your grip too much, then you will tighten up the muscles in your hand. A tight grip can have a negative effect on your drawing. It might take a little trial and error, but your drawings will quickly improve when once you find the right amount of grip that works best for you. Give it a try. It might surprise you.