Here’s a simple setup high key portrait with window light and a white reflector. Using a white reflector on a light stand behind the subject as a background I had him face the camera and the large window. With my metering set to spot I was able to blow out the background to white and property expose the subjects face.
What’s this reflector thing you’re talking about?
A reflector is a flexible, usually round shaped material that comes in a variety of colors. Silver, white, and gold are most common but they can come in green, black and translucent. Five-in-one reflectors allow you to change the reflective color to suite the situation. If you don’t have a reflector a piece of white foam core will do the trick.
The telltale way of finding out how a shot was lit is to look in the eyes to see the light source. In this case you can see the specular highlights from the window light and my reflection in the subjects eyes.