For this scene I used 4 lights. A sky light (intensity 0.3) for the ambient, a directional light that will affect just the diffuse, another one just for the specular, and what I will call "red light" for the back light. This way I can move my "spec" light to have exactly what I want.
When I have all my lights I do a grey render to check if it's what I had in mind.
I'm not really sure about the back light intensity and I don't want to spend too much time adjusting the light. So I turn it a RED colour, turn off the other lights and do a render.
I will use this render later on in Photoshop by selecting only the red channel, copying it on a new layer and turning it to white. I will be able to play with the light intensity directly in Photoshop instead of 3dsmax.
I do a render with the textures activated and the RED light off. At this point I don't care about the colours and the contrast because I plan to tweak everything later in Photoshop.