Hello All,
In this first picture you can see where my subject is and where my main and fill light are located. Main is on the left and fill on the right. The second pic is a close up of the subject so you can see how the lighting falls on the subject using the modeling lights to determine how the shadows will fall.
When I set up my lights, I know what I want my main light to be so I will figure how many stops difference I want the fill and main to be and meter my fill light to the lower f stop I want it to be while the main light is turned off. Once I have the fill light metered, I will turn on the main light and adjust it until I get the F stop reading I want. When I meter the main light, the fill light stays on and is included in the metering of the main. This gives me a more accurate reading. Of course you do have to take into consideration the skin tone of your subject. If it is a dark skinned person then you may want to open up your f stop by half or one. If it is a real light skinned person, you may want to stop your camera down 1/2 to one f stop.
This picture is of the subject using both the main and fill light. You will notice that you can see the shadow is light but still allows you to see contour of the face.
This picture is of the subject just using the main light and no fill light. You will notice that the shadow is darker and more defined.
To separate your subject from the background you could add a hair light or a background light. I did not show these as my subject has no hair.
I hope this helps.