Mark off the area you want to till by spray painting around its perimeter.
If using a rototiller, set the depth adjustment bar to its highest setting. This usually is located on the back of the rototiller, and sets the machine high enough to cut through the grass, making it easier to remove. A rototiller uses rotating blades to break up the soil.
Start the rototiller and run it through the marked-off area. Walk behind the rototiller and guide it; let the machine do the work.
Remove the turned up grass from the plot with a garden rake. Use a shovel to remove or break up any clumps that are sticking to the soil.
Lower the depth adjustment bar a few notches, then make two more passes through the plot. Lowering the adjustment bar allows you to dig deeper into the soil.