The simplest portrait lighting technique is called “Broad lighting”. This requires two lights, both with softboxes or brollies. With the subject sitting at an angle to the camera, position your main (brightest) light to one side of the camera so that it slightly above head height and pointing at the side of the model's face that is closest to the camera. Position your secondary light (or a large reflector) at about 90 degrees to the camera on the other side of the model's face. This light should be at about half the brightness of the main light.
Broad lighting is used for high-key portraits, and has the effect of making the model's face appear wider, so use it with anyone who has a thin face. It also de-emphasises features such as a prominent nose, and can also help to mask wrinkles.