There are numerous mistakes that are difficult to spot because they are so minor. A lot of the times, people find that their subject looks to masculine or feminine, or too young or too old in their drawing. Here is a list of things that may or may not affect the appearance of your artwork. Don't use everything that is listed, only those that suit your drawing the best.
Too Young or Too Old
People with longer noses then to look older. A lot of the proportional errors
happen here so this should be one of the first places to check.
Children have larger foreheads than adults. The hairline can be moved higher
for a younger appearnce, and lower for an older one.
Children have larger and rounder eyes, it is not recommended to change the
shape or size of the eye, but it is something to check for in your drawing.
Smile lines Dimples, lines, and wrinkles caused by smiling will make a person
look older if shaded darkly. Lighten it with a kneaded eraser if neccessary.
Under Eye Bags Alot of people have baggy muscles under their eyes, but when
it is shaded darkly, it will make the person appear older. To make someone
look younger, remove the shading with a kneaded eraser.
Femine and Masculine Appearances
This is a feminine characteristic, it makes the subject look like they are
wearing lipstick.
Thick, dark, eyebrows gives the subject a masculine look, while thinner eyebrows
with a sharp arch makes a more feminine.
Long, thick and dark eyelashes are feminine characteristics. Shorten and lighted
the shade for a more masculine look.
Men tend to have square jaws, but check your subject before changing anything.
Broad shoulders is a masculine look.
Avoid small waists when drawing men.
Dark Lips
Eyebrows
Eyelashes
Jaw
Shoulders
Waist