There is an art to making this determination, but a good rule of thumb is to avoid ambiguity. Built elements in a natural setting or wild intrusions into the built realm work well, but if it is not immediately clear whether you are in a natural place or a built place, then the balance is probably off. Decide on one style. If both a Moroccan-themed pleasure park and an English garden appeal to you, make the difficult choice between the two. 4. Coordinate the materials that you use.
Materials look best when they are related in texture, color and degree of naturalness.
Contrast can be interesting but should be done deliberately for a specific effect, not just to amass a collection of things that appeal to you. Maintain a high standard for construction quality. Likewise, insist on corrections from a contractor who has built something that looks shoddy to you. Keep it clean. Consider the ease of maintenance in anything you add to your landscape.