When building a new home, consider orienting the house to face as close to due south as possible to maximize solar access. If you want to have the option of installing solar panels for electricity (photoelectric cells) or hot water in the future, make sure that trees will not block the sun from reaching the southern roof of the house.
For a passive solar house, you should plant or preserve large deciduous trees (that drop their leaves) near the house to block the summer sun and provide for passive solar heating in the winter. Long eaves on the south side of the house can also block the high summer sun from heating the inside of the house while allowing the low-angle winter sun to enter the house to warm slab floors that will radiate heat long after the sun goes down.