This is hopefully a tutorial covering some basics of lighting in Maya, utilising Mental Ray.  I made this tutorial for someone in a forum and tried to replicate their scene to better show them how to control their lighting.  So while I wish I had some more detailed models in there to demonstrate with, such as the head, I used what I could find that was shaped most like the stuff in their scene, rather than what looked best.  I don’t consider myself great at lighting or anything, but I noticed a lot of people seemed to have issues with artefacts in their shadows, or lighting set ups that make it looks like it has artefacts, or they can’t soften their shadows, so I figured I would try to help out.  There’s probably some better ways to do some of this stuff, but this is what I have to offer, and hopefully I’m not providing any incorrect information.

Three-Point Lighting:

I will start off on the concept of 3-point lighting, as I understand it.  The three light points are typically referred to as Key, Fill and Back.  We will cover this all again when we start lighting, but first we have an overview so we are working with the same mind set.

1) Your key light is your main light source.  Sun, lights above, spot lights, etc.  This is your main light source.  Often it seems like people aren’t sure where to put this light and will toss a light wherever and often in places that make no sense.  In a case like this you may want to tell yourself a bit of a story if you're trying to get it to blend into a scene nicely, and figure out where this light would be coming from in the scene.  It's possible it's just lighting you set up for a beauty shot there, but try to think of it like how you might light it in real life.  But anyway, the key light is mainly where your light is coming from.  Pick an angle that defines the features of your model well, if you can.  Sometimes you pick realism over design, but I suggest that whenever you can, since artists are often trying to show off their work, light at angles that are going to cast shadows and catch highlights in a way that best defines the features of whatever the focus of the scene is.

2) Your fill light is off to the side and is again used to help display the details of the model, rather than hiding it in hard shadows.  It simulates the way that light typically diffuses across an object.  In real life light diffuses across a surface and we have bounced light, etc.  So sometimes, in lighting a shot, we're helping to accentuate that, which is generally what I use a fill light for.

3) Your back light is used to break the image up from the background.  A lot of people tell you that your key light is your brightest light source.  Often I have my backlight just as bright, if not brighter, for my back light (but not always).  The idea is to get just that bit of rim light on the back to break up the model from the dark or similar spots on the background.

Now, while it’s called 3-point lighting, there is often a misconception that this means only 3 lights in the scene.  Nothing could be farther from the truth!  3 points refers to 3 bulletin points.  It’s not the light itself that is important, but the concept that the bulletin point is trying to execute.  A better way to think of the three points of lighting is like this:

1. Set up lights for your main source(s) of light
2. Set up lights to diffuse the light from your key lights across the surface of your models
3. Set up back lights that help break up the model from the background and give them added depth

So even though it’s called 3-point lighting, it’s very rare that we ever use only 3 lights.   In this tutorial, as we go, we will have other light sources from a background image that isn’t accounted for in the lighting of the render that we will have to emulate.  There will be a bounce light from a floor that isn’t there, so we will have to add it ourselves.  So these are all lights I will add after my 3-point lighting (though, depending on the scene, they could just as easily be part of the 3-point lighting too.  Really, any light you add tends to add to one of the points!).

Setup:

I remade this scene with an old, ugly head that looked similar in shape to the head I was comparing when I made this tutorial, and I remade the pedestal.  The background is an image plane attached to the camera.  Whilst not the prettiest thing, it’s enough to catch light well enough to demonstrate the process.