Drawing figures is more than just copying. To blindly copy is not learning at all. Drawing is more of thinking. As Karl Gnass said, "Don't copy what's incomprehensible, ambiguous and unclear to the eye if it weakens your visual statement". You want to ask yourself, what action is the model doing? How will I put that action down to my paper? I know it is basic, but it is essentially vital that it takes couple of seconds to resolve it in your nuggin. Know your strategy. You would want to look at your model's torso and pelvis, it's turns and twists, and to where it is facing. Forget about the measurements for now. You want that ACTION down! Basically, landmarks like the sternum, and the anterior superior iliac crest or ASIS (please check your anatomy) are pretty much your guide to tell you how much twist and turn, granting your model is standing up.
Your next question is, where is the weight being distributed, and how are the other parts, like the extremities, and the head are responding to that gravity? If you're not sure, do the action yourself. After such investigations, you should be equipped to get it down to your paper. Make sure these points are clearly express in your drawing. It's what they call "gesture". It won't come easy at first, and if your figure looked stiff, something is wrong and you know you have to work it out. Fluidity is the operative word here. There are more details on such techniques, and I suggest that you invest on instructional books on figure drawing if you're serious into learning. You'll discover and learn a lot of stuff as you would learn from a class. Have some patience and you'll get it.
When you feel confident on your skills get some art classes for serious artists, not those kiddie classes in your neighborhood where you would only be embarrassed by some, still in their puberty, who are way talented than you. Adults are generally more discreet on this subject. Moreover, you don't want to waste so much money on trying to learn from scratch like you have never done drawing before. Come prepared. Figure drawing offered in community colleges are not that bad. When I started signing in for art classes, I was confident enough of my drawing and the stuff I learned from instructional books ( just have minor kinks that needed to straighten up) and it makes learning easy, fast, and not overwhelming. I always believe that talent, regardless of what they are, can always be acquired. If it is innate in you, then it becomes easy and natural to learning; and more so with proper nurture, it can even blossom to ingeniuty and mastery.
The drawings above are not that all perfect, but at the end of the exercise I ask myself those same questions to make sure that I was clear in expressing gestures. Can you feel the weight of that head resting on that model's right hand? Get busy!