Permaculture
Even if you don't grow your own food, the prinicipals and concepts behind closed-loop system like permaculture saves water and resources in the long term.
For example, I don't grow annual flowers on the most part (I have one small pot on my front steps with some annuals that my kids take care of). Otherwise, I grow perennials, whose deep roots means less watering. I also put down mulch in my flowers to help retain moisture (and keeps down weeds). I also select plants by their usefulness at times - things like chives and walking onions not only add interest to the garden but are yummy as well!!
We also collect rain water and use that almost exclusively to water our food gardens and perennials. We so far have one 1000L tank, and I hope to have 2 more by the end of the summer.