here is how you draw people (specifically that reference)
the important thing to learn is how to think in 3d. your subject is not a 2 dimensional being; it exists in 3 dimension, meaning to say it has volume. as such, perspective has a drastic effect on what your drawing looks like (things closer to the 'camera' are bigger, things further away, smaller).
whenever you draw anything, make sure not to focus too hard on any single portion of the body at one time. create an outline, a basic stick figure, then start to layer on portions of flesh. if you focus on one portion (like say the face) and then add the rest of the body as an afterthought, it's not going to look good, and you'll either have to readjust things constantly or end up with an off-looking image.
my suggestions: study anatomy really hard. look back and forth between your subject and your piece CONSTANTLY. but always remember that you're not just copying lines, you're chiseling out shapes. think like a sculptor. develop a 3d understanding of human anatomy.
PS: good drawing skills will translate into good pixelling skills. give it a shot.
you can apply the same techniques for the human face:
(this one doesn't demonstrate it as well as i remembered; i'll try to find another example i made that shows plotting out the facial features)
just plan out everything before hand, develop a base model, and then start adding stuff on top. easy to spot mistakes before you get too far, ensures anatomical accuracy.
limbs (ie arms and legs) tend to start thickest nearest the torso, but they usually start to taper off as they get nearer the joints (elbows/knees). the joints sort of bulge out, then taper off again till you reach the extremities (wrists/ankles).