In oils, there seems to be two different approaches to mixing your colors for a painting. One is a direct way where you mix it as you go. The other you pre-mix a certain amount of colors that your going to use before you apply them.
With a tight drawing and the values thought out, there's less guess work on what are the appropriate value relationships when you mix the paint for one area compared to another pre-mixed area.
It seems like most artist blockin their paintings either by first one monochrome color (burnt umber, etc.) for values or they block it in with the overall color of certain large areas (for example, a potrait, the face is one color, the hair is another, the background and so on) for color and value at the same time. It seems that most artist that mix the color blockin for one area, come back to that area and focus on it pre-mixing a "few" colors at a time? If you didn't blockin different areas first and just focused on one area at at time (like this Gurney post for example), how do you pre-mix your colors?
How do you determine how to start mixing the appropriate colors? I mean, do you determine what the local color would look like under certain lighting conditions and start mixing the lights and darks? Or do you start by the middle value, mix lights and darks and then adjust hue and intensity as you go? Or, do you try to think of what kind of lighting is being used and try and get the overall hue and intensity of the object, then mix light and darks? Or is there something I'm missing altogether?