I would like to draw your attention to a book. It is the Portrait Photographer’s Handbook written by Bill Hurter.
This book about, you could have guessed, portrait photography was not designed for the absolute beginner photographer and I really doubt that it would be regularly flipped through by the experienced professionals. The target audience is somewhere in between:  it might be useful for those who have already made a few portraits, started doing the Photoshop magic and would want to develop their skills with the desire of being able to make powerful portraits.

The handbook starts with explaining the equipment and basic techniques necessary for portraiture touching topics from focal length and depth of field of lenses, through file formats (RAW rules) and noise filtering, to studio strobes and light controlling tools.
These things are important parts of the foundation of portrait photography however, most of these details can be found on the Internet with some googling.

Posing, as it is a critical component of portrait photography, is also discussed. The fundamental thought is that rules of rendering the three dimensional human body into a two dimensional picture have been refined over hundreds of years by artists. These rules are not be followed to the last letter but are important to know, understand and leverage them because they provide a basis of showing the human body at its ideal fom.

The author mentions the basics of picture compositions as well: the rule of thirds and the golden ratio and lines as picture elements driving the attention of the viewer.

Lighting is a bigger topic discussed through more chapters. We can read about the kind of industry standard portrait  photography lighting patterns, the different ratios of key and fill light, and also about how a photographer can leverage available ambient light outdoor and how it can be combined with artificial lighting.

One chapter is talking about correcting face or body irregularities by smart posing and lighting, and an other touches upon some Photoshop tips.

The book is full with great – but, according to some critics, somewhat too sweet and American – portrait photographs and we can read a short technical explanation of how each picture was made, what techniques have been applied.

The Portrait Photographer’s Handbook might not be the best books for everyone, but is definitely worth a reading for the not-that-beginner portrait photographers.