Yeah, then you should study, study, study, draw, draw, draw until you get it right. But if you can’t afford that, there are always ways around. One of them is described below.
Note: this tutorial assumes you have basic skills of searching additional information. Not every detail is described.
So, instead of making sketches out of nothing, or using some random images as reference or posing your drawing dummy, you can pose 3d model and use it as ref.
Step one: makehuman
Because not everyone can or wish to model from scratch just for posing.
I’m not going to go in details because interface is mostly straightforward. The only thing you need to pay attention apart from actual modelling is exporting: make sure bones are included in pose/animate tab and export in blender exchange format.
Step two: blender
You may need to install makehuman import plugin which is available at makehuman download section.
Then import the model, edit it if you want and pose. I recommend using posing library if you are going to need multiple poses.
After you’re done with posing, maybe adding something to the scene and placing the camera, all you need is render. You may want to use ambient occlusion if you don’t want / don’t need proper illumination to be on render.
Just grab your graphical editor, import rendered image and draw your sketch!
You’ll still need to do the rest of the job yourself :p