Group plants by their requirements for water, sun, and soil.
Choose plants adapted to your garden conditions.
Plant pest and disease resistant varieties to reduce the need for chemicals.
Go Native! Native plants thrive with little care, with the right conditions.
Minimize lawn areas. Most trees, shrubs, and groundcovers need less water and fertilizer.
The Farmer's Almanac has examples of four easy gardens designed for different site conditions: A Garden for Hot, Dry Conditions; An English-Style Cottage Garden for a Sunny Site; A Garden for a Sunny and Damp Spot; and A Garden for Light Shade.
To go native, check out Washington State University Gardening. This website will help identify and imitate nearby native plant associations, or to start from scratch to establish native plant associations appropriate for your site conditions.
In need of inspiration? Visit one of the public gardens that feature native plants. Here is a list of gardens and other native plant resources from the Water and Land Resources Division of King County.
The Waterwise Garden at the Bellevue Botanical Garden, not only has great gardens to look at, but has a lot of educational material available at its visitor center.