Turn on the rototiller.
Adjust the rototiller's tines to a shallow depth if the machine features height settings.
Make several passes over the area with the rototiller to loosen the top few inches of soil.
Examine the ground to determine whether or not it is level enough for your purposes. You may need to shovel the loose soil away to examine the area.
Repeat the process of using the rototiller and examining the ground until the ground is level enough.
Smooth small bumps in the leveled ground's loosened soil with a steel rake. Leaving the soil in a rough state can lead to more clumps and bumps than the ground had originally.