Sometimes we get lost in the technical side of things. My advice to beginners in the field of portrait photography is to keep it simple. Focus on coaching the subject. That is the main thing that sets the work of a professional apart from the rest.
On the technical side of things, there are several approaches.
You can spend a lot of time experimenting with the light setup until you find the ideal placement of the lights, the background light and the subject in relation to the lights. As soon as you have nailed the setup, take notes so you can replicate the setup in an instant. Now, when you get the subject in front of your camera, you don't need to worry much about the technical side.
You can also keep it really simple and use natural light (like Peter started with). That also eliminates the need to worry about technical things like how to set up lights and light stands and the background light and so on.
Do you get my drift? Keep it simple. Focus your attention on the subject. Click. Repeat.
[The attached image was shot today using one light source. Guess which one.]