This is difficult, but definitely possible by breaking it down into manageable steps.
Start with the gesture of the pose (easier to figure out with pencil and paper). Don’t get too cerebral at this point because you aren’t trying to make an accurate drawing, you’re trying to capture the energy/life of the body. Get a feeling of where the weight is centered, any twists in the body, long lines of action, or places where the body crosses over and obscures itself. Use simple shapes and don’t be afraid to get scribbly. Don’t be afraid to alter the gesture if you’re referencing a photo. Study the silhouette.
Once you figure out a gesture that you like, start to construct the simple forms/volumes of your subject. By simple volumes, I mean spheres, cylinders, boxes, cones, and the like. For example, a head might be a sphere (with a jaw at the bottom), an arm or leg might be a cylinder, hips or ribcage might be boxes. At this stage, be sure to think about the direction things are facing in space. Is the thigh facing towards or away from us? Is it facing left or right? Up or down? Human-like bodies are very complex, but if you break them into pieces based on basic shapes/volumes: the head, neck, ribcage, midsection, pelvis, upper arms, lower arms, hands, upper legs, lower legs, and feet; it becomes more manageable.
Finally, you can add color and detail on top of your established structure. With small pixel art, less is often more, so you want to look for main establishing features. What features define the look of your subject? Which features could you imply, or live without?
Sorry for the somewhat long and potentially overwhelming process, but it can be used to draw literally anything you want once you get the hang of it. If anything is unclear let me know and I can try to explain better, since I’m unable to draw some examples at the moment.
