The shape and density of a tree's canopy determine how much shade it will produce. Shade as much of your home's roof and walls as possible. Dense shade over a small area is not as effective as weaker shade over a larger area. Wide-spreading trees are best for western exposures. Remember to leave at least five to ten feet between a tree and your home to protect the foundation from root damage.
Windows transmit heat much more quickly than walls and benefit more from shade as a result.
You will benefit from shading areas around your house as well. Driveways, patios, and other large, paved areas and gravelbeds store heat, especially if they're dark in color. If reflected onto your home and yard, this heat causes glare and increases temperatures. To reduce these effects, surround the areas with shrubs and grass. Vines and climbing plants are effective sunscreens as well.