Soon it will be time to cut your warm-weather perennials back almost to the ground, if you haven't already -- and with all those flowers and foliage out of the way, you'll probably see a lot more of your garden than usual. But what, exactly, do you see?
If your garden were exclusively perennials and annuals, you wouldn't see much more than bare ground. On the other hand, if you've got evergreen shrubs, statuary, sculpture, or structures in your landscape, your eye would have plenty of places to light on. These are the "bones" of the garden: the elements that remain constant even as the plants around them grow, change and die. They bring form and order to your space, and they inspire the imagination even as their context changes.
As you cut back your garden, keep an eye out for spaces that have a "barren" look or feel to them -- these are the prime candidates to receive a little bone structure. Other opportunities exist at bends or forks in pathways; intersections of sight lines (from two different windows, for example); or the perimeters of entertaining spaces. But be judicious in your choices: too many focal points, and nothing will stand out.