First, consider rainwater harvesting. Christian Keinapfel, an architect with Paravant Architektur, writes: “Collecting water from the roof is most of the time the simplest form especially if you have an existing building with rain gutters – the classical rain barrel.”
There are also companies out there that offer more sophisticated systems, which filter roof runoff and store the water in tanks. It can then be used for irrigation or for flushing toilets as part of a greywater system.
Those with concrete driveways or pathways around their homes may also want to think about installing porous (or permeable) pavement, which allow liquids to pass through them and are thus an excellent method to use stormwater on-site and minimize the environmental impact of pollutants (such as engine oil or antifreeze from parking lots) carried by storm runoff. Check out this Q&A for more details.