Sketch in more details, and start making the lines of the face and features sharper. Make the eyebrows thicker--you may want to draw them as thick, black lines, or you may want to draw the outlines of them. Add detail to the ears and notice how the cheekbones slightly protrude and how the jaw extends; the curve of the jaw should be a little lower than the mouth. Draw a male's jaw wider than you would a female's. Add a line for the bottom of the lower lip; if you like, add a thin, top lip. Loosely sketch where the hairline will be, noticing where it indents on the sides (I prefer to draw males with a widow's peak, in order to make the features angular).
Front: Note how the chin is the same width as the mouth.
Side: Notice how the eye is shaped similar to a slice of pie.

Add irises and pupils to the eyes. Add lines for a neck, keeping the neck wide.
Front: The neck should be slightly less wide than curve of the jaw.
3/4: The front of the neck should extend almost as far out as the middle of the nose. Notice how the back of the neck curves from the ear.
Side: Note that sometimes the entire jawline does not always stand out in contrast to the neck, but it stands out more often in men than in women. Note the line from the chin to the throat, which is often less pronounced in men than in women, due to the neck being thicker.

Sketch the hairstyle of your choosing. Sketch the hair in masses, not as individual strands. If you feel the need, sketch some arrows in the direction the hair falls, curves, and curls. Keep in mind that hair grows out from the head, then gravity pulls it down. Hairstyling and type of hair both play an important roll in how the hair sits. Notice how the bangs in the example curve around the forehead, and can be hidden depending on the angle of the head.

Add detail to the hair in a manner of your choosing. Some people like to draw strands all the way from root to tip, some people like to draw a bunch of short, individual lines, some people like to concentrate their lines in the areas of more shadow. Note how hair often frays a bit at the tips.