The lines are generally made up when the nose terminates at the bottom of the eye. This generally occurs when the face is very flat to one side, just enough to see the other eye. Most characters have either long or no sideburns in comics, and if the sideburn is short, it's just a shading ofcolour besidesthe ear. Some people have hair long enough to cover their ears, so ears become a moot point. Ears are generally one curve inside the other, and then the rest is pretty simple.
Hair is what makes or breaks a person's facial features.
Good drawing of hair will make it worth your while. If you look at pictures and use them as reference points, most of you might notice that sometimes, the outlines of the eyes and eyebrows can be seen underneath. This is up to you. I generally draw the eyes first, then the hair. It's better to draw hair segment by segment,rather than one big lump then segmenting it off.