When drawing a figure to proportion the professional way is with 8 head height. For beginners I recommend the 7 1/2 height. What I mean by this is that each figure or drawing will be 8 or 7 1/2 heads high (ex. If you draw your head 1 cm in length then your figure will be 8 cm or 7 1/2 cm in length).
Step 2: Body
When drawing the body you should create a line down the middle of your page. If your head is 1 cm in length then you will draw your line 7 cm in length. Measuring 2 cm in length downward from the chin of the head make a small dot/mark. From the height of your chin draw a horizontal line going 0.5 cm away from your head ( if you have a different size head then measure half of your head, draw the line to where the cheek and chin line meet on a 90* angle then draw the length of half your head outward following your chin line). Create a triangle from the dot to your chin line