One of the most effective types of lighting for portraiture is diffused window light. It is free, it's flattering to any subject, and it's available every day from sunrise to sunset. Make sure that direct sunlight is not entering the window. That creates too much contrast and very distracting shadows in almost all cases.
For the portrait you see here, my subject was sitting at a table and facing out the window that was approximately four feet from him. Window light is not that bright, so I used an ISO of 250. That gave me a shutter speed of 1/60th of second at f/2.8.
Notice the dark background. That helps to direct all of the attention to the subject. Nothing in the background is distracting or visually annoying. In my opinion a dark or muted background behind portraits helps create the best images.