Its easier to think about drawing the body if you break it into parts and then picture them as shapes. The head can be round or oval, the lips are triangular, the palm of the hand is like a square. When you are preparing to draw a face assess the basic shape, draw it then mark out the centre line. Mark in lines that will place the nose, the eyes and the mouth in their proper locations. By doing this the facial features will have the proper perspective.
When drawing the facial features note that all the parts have various characteristics.
The eyeball consists of the cornea, iris, pupil, retina and the outer part has the eyelid and eyelashes. the eyebrows form a frame over the top.
The nose comes in many shapes and sizes consider its size in proportion to the rest of the face.
The mouth depends on the age of the subject, the lips of a baby are puckered and relitively small, the young childs lips have developed somewhat and are fuller. This continues into adulthood only to thin again in old age.
The ears are rounded and curve like a shell, earlobes can be short and fixed or longer and free, some sit close to the head others stand out.
Look carefully at all the features taking notice of all the finer details. Practice drawing the various parts individually until you feel comfortable with them. then put them altogether to form your portrait.
Keep Smiling 
.