Insulate your attic space, and install attic vents and fans to help move hot air out of your roof space. Hot air can get trapped in your attic, keeping heat inside the building structure and making your air conditioning system work harder to cool the interior.
Insulate your garage door, especially if your garage is directly attached to your house. Heat transfers through garage doors more easily because they are typically lightweight and uninsulated, causing the interior of your garage to be hotter than the rest of your house and transferring excess heat into living spaces.
Replace single-pane glazed windows with double-glazed, low E windows and doors. Double-glazed windows consist of two panes of glass with an air gap between, providing greater insulation and reducing heat gain through windows.
Install blinds on windows, and provide as much shade around your house as possible. Patio covers, awnings, and exterior blinds all help exclude heat without eliminating light entering your house. Plant trees that will grow to shade your house, especially if they are located on the south side of the house where the sun is most intense.
Consider adding a layer of rigid insulation to the outside of your exterior walls if you are re-cladding or stuccoing your house. This would go under the new cladding or stucco. Greater exterior wall insulation will keep heat from penetrating through exterior walls.