Do your homework
Before you meet with a landscape designer, gather together photos that you like of projects from your neighbourhood, magazines and websites. You might find yourself pulling together a variety of projects, but a good designer will be able to pick out the common elements between the projects and establish your taste. My personal favourite website is www.houzz.com
Talk it over with your family
Discuss your ideas with family members, especially if it's a backyard project. How do they envision the space? There are many things to take into consideration, including lawn requirements, entertaining areas, pools, hot tubs, play structures, shade and garden sheds.