The first stage in any design process is to establish the "Elements" for your landscaping space. Obviously, this varies depending on the size of your area, the level of the ground, the site's characteristics, the soil, and any existing features that may need to be taken into consideration.
As the landscaper, you must sit down and make a preliminary layout of your area, including any permanent objects you might need to work around (eg. a manhole cover). Making a rough scale map of the region you have to deal with is something I would advise.
You may begin organising the plants and hardscape materials once you have your basic layout (be sure to make a few copies). Features are referred to as Hardscape and Plants.
Features are any physical characteristics that may be expressed visually through line, form, colour, texture, and visual weight.