Study the views into and out of the site, slope, soil, the sun and shade patterns, existing vegetation, structures and utility lines.
Note the positive aspects you would like to enhance and problem areas.
As you think about the design, try and find solutions to these problem areas and how you can utilise the positives.
The best landscape designs are those that draw fully from existing features. Ask yourself how you are placed with regard to maintaining your garden in the long-term.
Will you have the time and money to take care of a high maintenance garden or do you need one that needs minimal tending?
Get cost estimates for everything you would like to have on your garden.