Lawn grass can be dug up in strips, rolled and trucked away, but this method is slow going and difficult. Similarly, you can kill grass by pulling it up or tilling the soil, but neither of these methods is exactly a walk in the park. If you want to kill unwanted grass without a lot of time and effort, you will have to destroy it where it stands rather than pulling it out or driving it under the soil with tilling.
Mow the grass. This step is not necessary but will make whatever you put on top of it sit flatter.
Find a material to lay over your unwanted grass. Black plastic, newspaper, landscaping fabric or anything that comes in sheets and blocks light will kill the grass.
Spread the material over your unwanted grass. If you are using newspaper, apply at least three layers to block out all light.
Cover the sheets with something to hold them down. Spare bricks or rocks will hold down the edges, holding your grass killer in place.
Leave the sheet in place for at least two weeks. After removing the sheet, your grass should be dead.
Choose a liquid grass killer. Boiling water will kill grass and other plants without damaging the soil, but be sure to get it on all the grass. Pure vinegar will also kill grass, as will herbicides.
Pour your liquid grass killer evenly over all your unwanted grass. Be sure to not get it on plants you want to save since both hot water and vinegar are toxic to plants.
Wait three days. Most of the grass should be dying or dead by that point. Reapply your liquid grass killer to any grass that seems unharmed.