Choose light color vehicle: That still helps Choose vehicle with smaller window or windows have more verticle angle. I hope I am not going too far. Tint windows: watch local law, some area you may not do that on all windows. Maintain AC.
Keep enough fluids:
Wash water Engine coolant Brake fluid Engine oil: It's good idea to change oil more often if weather is really hot. Check oil quality by its color.
Park under shade, use covered parking if possible. Park under tree is a good idea but you may need to wash your car more often since trees and small animal leave harmful chamical to car's skin Vent cabin: Its a good idea to vent when weather is hot Use dashboard cover: believe it or, dashbaord cover really cools. Link Use sunshade: Like I can't state that enough. use our xshade and cool better.
Check tire pressure: do that when there is an weather change. Like from cold to hot, hot to cold. Always maintain proper pressure Check brake pad: Brake tends to fade more quickly when it's hot.
Drive less: reduce exhaust gas and help prventing global warmming. We are using too much gas/oil already. Link