Choose the location of your flower garden. Since so many aspects of your garden are dependent on the local landscape conditions, you need to know where you want to plant it before you begin your layout. Avoid places that are often very damp, as well as planting your flowers at the base of a tree that casts heavy shade --- few plants can do well under such conditions. A location that can easily be seen or that serves a specific purpose, such as covering up the foundation of your house, is ideal.
Sketch a rough plan for your garden. Determine the shape you want. A rectangular bed is easier to mow around, but a curved outline is more visually interesting. Fill in the sketch with color, using complementary tones to make your garden vibrant, and adjacent colors for subtler contrast. Figure out how high you want the various parts of your garden to grow. If your flower garden is against a wall or fence, putting climbing plants in the back is a good idea. Planting the tallest flowers in the middle is best for gardens that have walkways on all sides.
Choose the specific flower species you want to use. Select flowers based on several characteristics: their suitability for your climate and soil, the amount of shade allowable, color, height and months of blooming. You can plant flowers that bloom at different times of the year in the same bed to get a multicolored show all year long. Draw out a detailed plan for your garden, including the exact placement of every plant.