Choosing the plants.
Create year round interest, by planning a flowering calendar, this will enable you to have blooms spring, summer and autumn. Include in your design evergreens and shrubs that have interesting leaf / stem shape and colour, to add interest in the autumn, winter and early spring.
Larger shrubs take less time to get established but are typically more expensive to purchase.
Choose plants that are suitable for the environment that they are to be grown, i.e. shade loving plants out of the sun, moisture loving plants in wet areas, wind tolerant plants in exposed areas, etc.
Plants will inevitably grow so although your initial planting may look sparse, the plants will merge together when they become established.
When you are designing your borders you'll want to base it on a theme, be it hot colours, pastel colours etc. After planting up, remember these themes when buying or receiving new plants.