>>7644890
>>7644829
Line weight is something you will master as you draw more; the more information you have about a subject, the more of an instinctive 'feel' you will have on what to emphasize.

A general rule, though, is that outside silhouettes have heavier line weights. When you begin to understand anatomy and planes, heavier line weight emphasizes the overlapping of forms or the protrusion of bones. Line weight, however, is usually an afterthought. You will pick it up the further you progress.