Simplified Drawing for Planning Animation by Wayne Gilbert
There are thousands of animators who are extremely talented artists. There are also thousands of world-class animators who couldn't draw a straight line with a ruler. But the fact is, drawing is a skill, like any other skill. This means that it's not a 'gift' like some people think, it's a skill that's been honed over many sessions of practice. The gift you give yourself. Over the program's duration we'll present you with many opportunities to enhance your basic drawing and develop the skills that will assist you with your animation.
Simplfied Drawing for Planning Animation by Wayne Gilbert is probably the best, specialized drawing practice book
available to develop the drawing skills for character animation. It's unique path allows for simple, gradual understanding and improvement, and is considered a classic amongst animators today. Do exercises in the book a little at a time and as often as you can. You'll see your skills improving in no time.
It's a very difficult book to aquire these days so if you weren't able to find a copy for yourself, here's a PDF version that'll do just fine.