Most gardeners enjoy over planting perennials. However, if you don't divide these every few years, they may become overcrowded. For less maintenance, leave more space between perennials and fill the spaces with annuals. After thinking about types of plants and developing a plant list, plot your master plan with pencil and paper. To see your plan, it's helpful to use a limber hose to lay out any new curves in your beds.
Curves are better visually than sharp edges and easier to mow.
Group plants with like light and soil requirements together. Unless a specimen plant, where you might need only one, consider placing three of each type together. However, too many plants of the same type create a monoculture, which invites disease and monotony. Remember, for best visibility and impact, plant small in the front with progressively larger ones towards the back. They will still bloom and draw your attention but will catch up with the larger ones by the second year.