Orienting your house to take advantage of natural heating or cooling is a good way to reduce operating costs.  For example, rectangular houses with large south facing windows and thermal massing can help to capture heat from the sun in the colder months.  For more information, see the U.S. EPA website.  Deciduous trees planted on the south side of these houses can block the heat during the summer, but allows the sun to reach the house during the colder months when the leaves are off the trees.