Shadows very much belong to the objects that cast them. Insofar as is possible they should be painted at the same time as the figure/table/chair/building that owns them, painted as an extension of the colour used for the shady side of the object, since it is from this side that the shadow extends. The proximity shadow, the area where object and shadow meet, is usually the darkest part. Often I wonder if the shadow owns the object rather than the other way around, as shadow areas act as an excellent link between objects and their patterns reinforce the abstract two dimensional composition of figurative painting.