From the Forums: Getting rid of grass?

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A query in the forums is, how do you get rid of that pesky lawn?

We have a small patch of grass in our front yard and a decent size lawn in the back yard. Personally we feel lawns are a waste of water and space so we'd like to eliminate the lawn in favor of ornamental grasses, stones, and other low water plants. We have planted a garden in raised beds which eliminated some of the lawn, but we're just getting started.
The question we have is how do you get rid of the rest of it?

My first thought was tilling the soil and then going over it with a roller drum, putting down some plastic, before finally covering it in stone. But how can I be sure the lawn won't grow back? Or, is this the wrong approach entirely?

Any suggestions?