Chiaroscuro: the treatment or distribution of light and shade in a picture.
It should come as no surprise to learn that there are few—maybe no—real secrets in photography. Instead, what you’ll find here and elsewhere on the Web are informed opinions based on experience blended with some stylistic preferences.
The recipe for producing available light portraits is well known and includes a few basic ingredients: high ISO, fast lenses, and slow shutter speeds. That’s it. You can sprinkle in some reflectors and add a dash of camera supports but the main components remain the same. It’s the creativity you use in blending all of these elements together that creates pleasant variations. Some photographers prefer softly lit images often diffused with filters but you may prefer sharper, more saturated images. The choice is up to you.
If there’s any secret at all, it’s learning how to see the light falling on your subject, especially the range of shadows and highlights within the scene—the chiaroscuro. The best way to improve your photography is to practice. Make sure that you shoot something every week so you get to the point where you don’t have to think about how to operate your equipment: You just use it to create images.
Don’t worry about producing masterpieces each time you got out; use your camera as a sketch pad to explore possibilities and don’t be afraid of making mistakes. Sometimes these “sketches” will be successful, sometimes not, but don’t worry about it and learn from your analysis of the images. As Yoda says “There is no try, just do.”