Once you have decided where to site your new garden, the next step is to prepare the area for planting. If you plan to establish your garden somewhere in an existing lawn, you must eliminate the grass. There are many ways to permanently remove grass from a planting area. The least invasive and labor intensive of these is with plastic over the area. Depending on the type of plastic you use, this will not only kill the grass, but sterilize the soil as an added benefit.
Water the area with 1 to 2 inches of water.
Lay sheets of black plastic over the area of grass that you intend to kill.
Anchor the plastic by burying the edges in 3 inches of moist dirt or weighing them down with heavy rocks.
Re-wet the grass underneath the plastic once every three weeks until the grass is dead.
Rake away the dead grass.