The traditional view of landscape design is a detailed drawing specifying the location of each shrub and flower bed. Every time you buy a plant you are engaging in the landscape design process, either intentionally or unintentionally. There are many unintentional designers everywhere. Many landscapes look like a collection of randomly chosen and haphazardly placed plants.
For your landscape design it is useful to have an overall plan, but designing on the fly is also good. A plan for equipment access could be a first thing. Then you should start with the focal points. You should also keep curves in check that will add interest to your garden. You can also add flowers to attract hummingbirds and butterflies, and several berry producers for the birds. Leave some empty space: If your garden is too crowded, it will be difficult for you to enjoy each plant. So leave some space in between or add an extra walkway, so you can walk around them without stepping on muddy areas.Make sure you have at least one tree that provides shadow, and add a couple of chairs underneath to enjoy it. You could accent your house as well. Once you are ready with the landscape design you can enjoy your garden.