Place a key light in front of and slightly off to the side of your subject. This will be the main light that lights your subject and should be the largest and brightest light in your lighting kit. The exact placement of the key light will vary based on the type of light you are using. Start by placing it about 45 degrees from the camera and adjust it as necessary until the desired look is achieved. A low key setup, where the intensity of the key compared to the fill is relatively close, is ideal for soft lighting.
Place a fill light on the opposite side of your subject as the key. This light will be less intense than the the key and fill in any shadows created by the key light. Place it lower than the key light and at about the same distance from the subject. You can use a bounce card to create a softer light. A bounce card is a large, white cardboard or foam board that will reflect any light pointed at it.
Place a backlight in back of and above the subject. This will provide a rim light to light the hair of the subject and separate it from the background. Adjust the placement of the backlight until a clear rim lights the edge of your subject.
Use the light meter to meter the scene. Take measurements for each light source to ensure that there is not a large variation of light intensity. To take a measurement, place the light meter at the placement of the subject under the light and aim toward the camera. Adjust the intensity and placement of each light as necessary. Use the readings from the light meter to set exposure for your camera.