If you are cutting your grass and you take the grasscatcher off cut up grass will sit on top of your freshly cut lawn. This is called mulch this will meet 1/4 of your grasses needs and will help hold moisture in the soil. This also acts a fertilizer.
Mulch can be made for the rest of your garden too! Find an area of dirt with nothing important growing. The best time to make a mulch pile is in the fall when leaves are falling. Throw any leaves or cut grass into the pile. Keep the pile moist and turn it over with a shovel occasionally. Also add weeds, twigs, and fruit/vegitable peelings. Tell friends and neighbors so they can contribute to the pile. A week or two later you will have rich soil.