Good landscape design includes placing plants in odd numbers for a natural informal effect. Start with a focal point, one stand-alone plant such as an upright evergreen or a flowering tree.
Mixing colors and textures, create groups of three, five or maybe seven plants of the same variety around your focal point. Sometimes a larger mass planting of the same variety will create a dramatic effect, and add balance to the overall design. Create movement in your garden by adding ornamental grasses that sway in the wind and enjoy the look throughout the winter.
More to come on this topic.