Over the years, my palette map has developed in the manner shown. Colors are placed according to which are used most frequently. You’ll find that I place multiple piles for colors used more frequently, especially Titanium white, to ensure I always have a clean go-to color. The only colors I knife mix in advance are greens and purples, to ensure I have a selection of two temperatures of each handy. Green and purples mixes are opaques, so are used only in the end of the painting, in the final stage, after the transparents are placed. The videos here on greens and purples will provide more details to you on those recipes.
At the end of the day, I never throw my paint away. I cover my paper palette with a piece of Saran wrap, gently fold it over and slide it into a drawer in the freezer. The paint will stay fresh for quite some time. When I’m ready to paint again, I transfer the piles of paint to a fresh piece of palette paper. You can see the full list of color brands I use, and the links to purchase those, on my web site under supplies by clicking here.