A portrait is a painting, photograph, sculpture, or other artistic representation of a person, in which the face and its expression is predominant. The intent is to display the likeness, personality, and even the mood of the person. For this reason, in photography a portrait is generally not a snapshot, but a composed image of a person in a still position. A portrait often shows a person looking directly at the painter or photographer, in order to most successfully engage the subject with the viewer.
Smithsonian National Portrait Gallery http://www.npg.si.edu/
Explore your composition, use the rule of thirds, do not center your subject in every frame.
Move in close, fill the frame with the face of your subject.
Move away and use the room to reveal who the subject is.
What are the hands doing? use the hands to direct the eyes. movement around the frame.
Black and white? its digital.
Red eye… bounce your flash.
Use available light when possible.
Avoid backlit scenes.
Don’t have the subject looking into the sun. They will squint at you.
Quickly fix skin tones in Photoshop.
How to Get Amazing Rich Skin tone with One adjustment / Photoshop Tutorial / Color grading
Another good Playlist https://www.youtube.com/playlist?list=PLQZIYWgYcQlYV6pjzLV8R5Znr1ZcMXqFn
50 retouching techniques
Correct red blotchy skin
These are some start points. Google portrait retouching and see what you find. Remember when looking at tutorials to evaluate them before you start using them. How destructive are they. Can you take the concept and alter the steps to be non-destructive and still accomplish the effect?
how to: Liquify -print slim down that subject.
ADOBE: Liquify Filter
Liquify at the Beginning or End of Retouching?