Bathroom Lighting seems to be one of the least important rooms people consider when it comes to lighting.  However, Lighting is extremely important in the bathroom for purposes such as shaving, makeup, showering, and creating a mood for the room. 

Vanity lighitng should be your top priority since these fixtures work the hardest to illuminate the head and face for grooming.  The most common mistake people make is putting recessed lighting directly over the mirror.  These cast shadows on the face, which make daily grooming rituals difficult.  I have had so many customers ask "me what is the best place to place your bathroom light?"  Vertical fixtures or sconces mounted on either side of the mirror are the best for casting even light across the face.  To eliminate shadows under the chin, eyes, and cheeks, fixtures should be mounted on either side  36" to 40" apart.  The center of the fixture should be roughly at eye level about 66" off the floor. 
Given the size and positioning of some vanity mirrors, sidelights can be impractical.  In this case I would use a bath light over the mirror.  It should be placed 75 to 80 inches above the floor.  You will want to face the light down so it washes evenly over the hair and face. 

The shower is the next important part of the bathroom that needs light.  If it is a small bathroom with a clear door then a light is not necessary.  However for larger bathrooms with shower curtains it is highly suggested to install a recessed light with a water proof shower lens. 
To add some ambient light a surface mounted fixture is installed usually in the center of the room.  This can also be replaced with an exhaust fan/light