It's a small thing, but surprisingly, really makes a big difference:

My husband and I have begun re-using the water in the kitchen after rinsing fruits and vegetables or washing the dishes. We capture the water in a re-usable container and transfer it to outdoors containers as necessary, which we then use to water our annuals and perennials (in addition to catching rainwater in barrels). This has almost eliminated the need to use the hose for our plants. I also use it for our indoors plants and they haven't noticed a difference! :-)