First, find a suitable location. Choose a spot you'll be able to enjoy that's close to a power source for the necessary water pump. To keep your water garden clean of debris and leaves, don't locate it under overhanging trees. Make sure your garden will get adequate sunlight, as most aquatic plants require four to six hours of sunlight a day to ensure healthy growth.
Don't install your garden at the bottom of an incline. Rainwater runoff could flood it, and fertilizer and other chemicals you add to your lawn could flow in and harm the fish and plants.
Create some rough sketches of your water garden to visualize how it will look in your yard. Consider space and time limitations. While smaller fountain-type water gardens take up less space, larger pond-style water gardens are often self-sustaining and require less maintenance.