Look at the negative space rather than the actual body of the person, and draw the negative space instead. This will create a much better silhouette for your drawings.
There are no straight lines in the human body. Each and every line you draw should be a curve. Make proportion boxes to help guide you when drawing the body, so you don't make one part bigger than the other.
Go to an art supply store and find a movable manequin. These show the right proportions for the body. Always look at the body as an assembly of shapes.
There are many tips for drawing a body . At first I have to look up total body for focusing details. Then we have to start a rough sketch for getting first impression and draw the areas to create a solid,weighty figure.