Beat the heat - make your AC work better
Replace your furnace filter with a new and non restrictive one, the more flow by the fan the better circulation. Don't buy the 3M super filters, Canadian tire makes a filter made by Duststop rated merv 6. Its a 3 pack for $19.
Ensure all your floor vents are uncovered and switched open. Close the basement ones to boost air to the higher floors. Air returns (usually on the wall) should have enough suction to hold a tissue when its on.
Outside your AC condensor (big noisy box with a fan) should have lots of air flow around it. Clean the metal fins that stretch around the outside of the unit behind the cage with your hose but never power washer.
Inside feel around the furnace for any cold air leaking out from around the unit or duct work. Seal only with proper hvac aluminum tape.
Call a tech if you feel like its not performing well as it can develop a leak in the refrigerant lines that reach outside but get a few quotes if they want to replace everything. It could save you thousands.