Make sure your condensing unit located outside is not covered up and free of debris.
Change your filter on your furnace. Dirty filters restrict air flow.
Don't wait for your house to "heat up" before turning on the A/C. It is harder to cool hot air than warm cold air.
Turning your thermostat down lower than 70 won't cool your house faster it will freeze up your unit and cause it to have to thaw out before it runs again.