Same Elements, Different Results; What's the Difference?

Hi All,
I am in the process of revamping my front yard. I am taking out the traditional landscape that existed and replacing it with something more suited to the Arizona climate. I have been studying many pictures and I have found some yards have a lush but natural appearance while others seem very contrived. They both have the same elements; rocks, boulders, granite, native plants, but there is an element I can't put my finger on that seems to make a huge difference in the finished yard. Are there any rules or tips on creating natural looking chaos? What makes a landscape look old and real? I think I have identified one; plants touch each other. I am sorry I can’t describe the difference I am looking for any better. I am hoping someone will have an idea what I am trying to convey. Thanks for your help.