I've been meaning to post what Burtzum and that fat kid have already recommended. I would add to that fat kid's advice that studying your hand keeps you sensitive to the "give" of flesh, which sensitivity you quickly lose as you miss time drawing from the nude figure.
For gesture drawing twist paper bags into interesting shapes to draw. the point of the gesture drawing is to capture the basic design, the arrangement of geometric shapes which comprise the pose, and as there is a basic design underlying all forms, you can do gesture drawings of anything when you can't necessarily draw from the figure.
Then there's getting 3 eggs, composing and lighting them creatively, then drawing them. As eggs are continuously curving forms, like the human figure, drawing eggs under these conditions keeps you sensitive to the play of light and shadow on actual flesh. Over the last 3 years I've been mentored by Jon Onye Lockard he's required me to draw LOTS of eggs. A couple examples are posted below.
I've done them with the understanding that the ovoid form readily analogizes for the head; also, I felt the creative challenge Professor Lockard was setting me was to continually find something interesting in such a seemingly boring, static subject.
But one day after my 7th or 8th egg drawing, which are admittedly looking ever less inspired, I was watching my A MIDSUMMER NIGHT'S DREAM dvd, and had a revelation when this shot of Rupert Everett as Oberon came on the screen. The egg isn't just for the head. Note the deltoid, the biceps, the fore-arm, the breast, the knee, the inner thigh; all eggs! The way light plays on the egg also gives you cues for lighting the ribcage below the shadow lining the lower edge of the breast, a detail flattened out and easily lost in photo ref like this.
One more thing; the egg drawings are conte, but before he assigned eggs Professor Lockard had me do copies of Watteau drawings to learn how to handle the medium.
"Three's so little room for error."--Elwell