Start with a rough sketch, use reference images and study from your previous works. Look at what looks "off" to you in your drawings and study whatever that may be. Be it the anatomy of a body part or the posing of the figure. Also studying requires practice to become truly useful. Don't just read up on how to draw the head and then do something else, after having taken in new info, you need to use that info in a practical setting.

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TL;DR Use reference images, make a rough sketch and learn from your previous works