This is in honor of Abby's backyard - here's the general process you take when planning a landscape.
1. Create a Base Map - House plans or a property survey are a good start. Measure the dimensions of your home and yard and plot them on graph paper (1 square = 1 ft.). Plot existing patios/decks, sidewalks and vegetation you want to keep. Indicate windows and doors. Also indicate overhead or underground utilities. We called a utility hotline to have all our underground utility lines marked. Make several copies to use in later steps.
2. Site Considerations - On a copy of the base map, indicate site conditions that will influence the design, ie zoning ordinances, topography, drainage, views to enhance (ie curb appeal) or block for privacy. Where will you need walls or walkways?
3. Functions - As in all design, you should think about function first, then form. In your backyard, will you be grilling, dining, lounging, swimming, sunbathing, playing on a playtoy or playhouse, growing fruit trees, growing veggies in a plot, growing flowers to cut, showcasing a collection of plants, creating views from your home windows, framing lovely views that extend off your property, screening ugly views, creating privacy, blocking hot sun or cold wind, watching birds or butterflies, playing catch or flag football or frisbee? When you have your list of desired functions, indicate with freehand bubbles what functions different areas will have. Play around a bit with different ideas. Don't worry about specific shapes or plants yet. Also draw where foot traffic will flow through the yard.
4. Borders - After figuring out where you want different functions (like outdoor rooms), create the borders of the different areas of your yard by using a general theme: square or rectangle shapes, circles, or smooth curves. Curves should be bold - avoid squiggles. Avoid narrow angles between converging lines. You might sketch several design ideas, using a ruler and compass or even bowls or cups to get the outlines you want.
5. Height - Build on your border design by considering the third dimension - height. Ensure adequate drainage by making sure the ground slopes slightly down from the house. Crease a sense of privacy and enclosure around gathering places with walls and/or ceilings made of shrubs, trees, vines or building materials. Direct traffic without blocking views with borders of low shrubs.
6. Materials - Select non-plant materials for terraces, walls, edging. These should complement the materials with which your home is built. Avoid using too many different materials. Consider maintenance costs when comparing prices.
7. Plants - First decide the size and general type. For example, you might want a row of shrubs about 8'T by 6'W along one side, a 20' tall flowering tree in a corner, a low groundcover in one area, and a perennial bed to fill another spot. Start with the largest and move to the smallest plants. Plan space for the mature size of the plant!!!! It's hard to believe that a tiny baby tree will someday grow to be 50 feet tall and wide, but it happens.
Of course you'll go back and forth between the steps a bit to make adjustments, but this is the general process.