After learning the basic construction of the Manga / Anime head, there are other important factors yet to remember. There are many different types of heads and faces to be constructed. Such as the difference between the male and female head. You should know what makes an Anime / Manga female head look so feminine compared to a males' head.
The only way that a beginning artist can develop the ability to see and then indicate correct proportions is to become acutely aware of proportions by observation and practice sketching. Unfortunately nobody can teach you this important phase of drawing. But you CAN estimate proportions and then check them with a fair degree of accuracy by employing what is called the thumb-and-pencil method of finding proportions.