Here is the progress of my painting "Temple Ruins" [link]
I always start with a low resolution grayscale sketch, which I refine until I'm fairly satisfied with the values. Then I add the colors in a separate color layer and continue the painting in color. As you can see, there's been a lot of struggle with the composition, which was modified until the very last steps. Lots of time was spent on trying to find the optimal layout, but I think the effort paid off in the end.