Study, study, study. If you truly want to make a masterpiece, you don't want to screw up on something near the beginning and not realize it until just about the end. Use reference pictures, techniques, other tutorials or pictures related to what you're drawing, in fact you can even open a new document, if you're using a program, and just practice before you go for it. It could make or break your drawing, so always be keen to make sure everything's alright. The image before you is a chart on the difference between masculine and feminine traits. This is VERY important to keep in mind when drawing human bodies because you don't want to mix the two up, or make something out of proportion. Now, males are much broader, more muscular than women. Their chests are somewhat flat, and shoulders much more broader. Their back, shoulder blades, show these traits as well. Much broader, thicker, bulkier. The pelvic area, though, isn't as large as a woman's. Usually when you do males, you'll want to make your lines sharp, and try not to make them too curvy. Women have larger breasts than males, a much curvier back, and much wider hips. When drawing women, it's key to make sure that your lines are curvy, smooth, and sharp. Curvy lines give the figure a very feminine feel, which means you could easily define the figure between male and female in the very first stages of your drawing.