What about the Background.

 A question came up on a artists' group. What do you paint first in a portrait, the subject or the background. Now I can tell you how to paint, but remember the background will definitely affect the look of the subject. Here is an example. I painted this sketch of a model on an orange toned canvas. (Don't do this at home) Here is the finished sketch. After looking at it a number of times over a month or so, I was unsatisfied with the over all darkness and dullness of the face colors. The brighter orange background in relation to the subject caused the color to look less vibrant and flat and made her face look just plain dirty needed a shave :)

Elizabeth 1,  5 x 7 oil

I decided to paint the background a darker tone. Still keeping the color warm, but much less vibrant than the orange. The colors in her face now appear much lighter and vibrant. Her pink blouse no longer fades into the background but becomes and element in the painting.

Elizabeth 2,  5 x 7 oil

So my answer to the question, what comes first the model or the background is both need to be taken into account throughout the paintings progress.