Composting is the controlled decay of organic matter in a moist aerobic (oxygen-demanding) environment Tiny organisms (bacteria, fungi and protozoa) break down organic material to create compost, which is a great source of nutrients for your plants and garden!
You can purchase different composting units at any home improvement store, or you can build your own. Elevating the bin a foot off the ground will help with drainage. The ideal size for a compost pile is 4'x4'x4'. Any smaller and the piles may have trouble holding heat, any larger and the pile may not be able to aerate properly. Start with a layer of "browns": leaves, straw or sawdust. This provides carbon. Next add a layer of "greens": grass clippings or vegetable scraps. This provides nitrogen. Add a layer of garden soil to each brown-green layer.
The pile should be turned from every 3-5 days or so and should not allowed to get too wet or dry. The pile requires both air and water. If the pile gets too wet, add some shredded newpaper to the mix. The top should be concave to collect rain water to keep it moist. If the pile has a bad odor, it may need more air, so turn it a few times and add some dry material such as straw or newspaper.
The pile should heat up to a temperature of 100-140° Fahrenheit. The compost is ready when it no longer generates heat and it's materials have turned to brownish-black. You can also add earthworms to the pile. They improve the nutrient content and the aeration and drainage of the compost. Earthworms like coffee grinds, breads and starches, vegetables, tea bags and non acidic fruits such as watermelon. Avoid citrus and garlic.
Information from: Clemson Sandhill Research and Education Center Midlands Home Composting Garden