Small yards in front of English Industrial Revolution-era cottages were filled with gardens that provided vegetables for the table and flower beds for a bit of beauty in an increasingly gritty urban world. "Classical" Italian or French gardens surround walks and terraces with lush growth and container plantings; Zen gardens use rocks and gravel to represent streams flowing through flowering shrubs and trees. Modern "natural" lawn-gardens feature wildflowers and other native plants. Whatever your choice, converting a lawn into a flower bed is a project for the gardener who would rather weed than mow.
Identify a focal point of the garden, usually a front door to the house in a front-yard garden, and lay out paths and other features like patios or water features to draw attention to the focal point, either by leading to it or placement near it. Once your flower beds are full, these "hardscape" features will create the voids in the garden that draw the eye to the focal point, be it a door, picture window or porch.
Lay out beds and cultivate the soil to a depth of 6 to 8 inches. Amend with at least 2 inches of compost mixed with an equal amount of manure or humus. Clean out every blade of grass and weed. Lay a sheet of black plastic over the space for two months to kill grass and weeds underneath, or kill everything with a nonselective herbicide containing glyphosate. Chemicals provide no short cut; most require letting the ground lie fallow while the poisons dissipate through the soil. Both methods require cleanup of the plant material that remains.
Level the soil with a rake and grade it so that excess water drains in the direction of storm drains or drainage swales that may run along property lines. Raise beds and terrace hills to retain water rather than shed it; the goal should be to use as much rain as possible for the plants. Plant moisture-loving plants in damp places for a "rain garden."
Plant trees and shrubs in your garden-lawn, too. They will provide background for plantings and shade for shade-loving plants and seating areas. Build raised beds as long as you like with landscape timber or cast stones. Make them narrow enough so that everything planted in the beds can be easily reached. In areas where beds are at ground level, add access paths for grooming and maintenance. Mulch paths with wood chips or shells over a layer of drainage gravel.
Arrange plants in groups of three, with tall plants in the centers of beds so that each bed can be appreciated from inside the garden as well as from the front porch or street. Plant beds with native plants when possible; they require less fertilizer and water than "immigrants." Mulch garden beds with an inch or two of compost or shredded bark to aid in weed control and insulate roots.