Drawing a nail is fairly simple. Female fingers are typically
slim whereas male fingers are more thick. Of course, a female
may have a thick finger when she is either a) portly (obese),
or b) she is masculine in nature. Don't forget: an obese
person's finger is more rounded.
As for drawing a nail, the length may vary from very short
to extremely long. If you look at the examples to the left,
you'll notice that they also differ in shape (some are pointed,
some curl underneath itself, some widen outwards, etc).
Drawing a finger at the side, you'll notice that the nail
goes downwards midway. Notice also that the nail may slightly
go up, slightly go downwards, or go straight.
Drawing a finger from the top, the nail is basically a simple
shape: triangle, rectangle, square.
Since the nail begins several centimeters from the end of
the finger, the nail will shorten considerably when drawn
(and viewed) from the bottom.