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Best advice you can get is practice, practice, practice.
I lack the hand-eye coordination to draw with any level of proficiency (my drawing turn out worse than yours, believe it or not) but I've watched people draw and there's actually a method to drawing anime in particular that people use which helps to improve proportions and maintain realism as far as body positioning and such go.
Break the body into a series of simple geometric shapes. Pic related, but absolute shit because I did it in paint (couldn't rotate, only flip/reflect) and because I'm a terrible artist, anyway.
Remember when doing this that joints must be connected (look at the shoulders, hips, and knees in my example). After you have a simple geometric figure like this, you add an outline to finish off the drawing.
I'll try to find a less shitty example for you.