Compost is a soil amendment created through the controlled decomposition of organic materials such as leaves, twigs, grass clippings, and vegetable food waste.
Compost is made up of four elements: nitrogen, carbon, water, and air. For nitrogen, add layers of green plants and manure; for carbon add layers of brown/woody materials–such as leaves, straw and mulch; hosing down and flipping your pile adds water and air.
Mixing certain types of materials or changing the proportions can make a difference in the rate of decomposition. Achieving the best mix is more an art gained through experience than an exact science. The ideal ratio approaches 25-30 parts carbon (brown/woody materials) to 1 part nitrogen (green materials/maure). Judge the amounts by weight. *Too much carbon will cause the pile to break down too slowly, while too much nitrogen can cause odor. The carbon provides energy for the microbes, and the nitrogen provides protein.
Keep adding layers of the different materials–each hosed down with water; you want the compost wet, but if you squeeze a handful of the mixture and water comes out, then your pile is too wet. Keep building the compost pile until it is at least 3×3 foot. Leave the pile sitting for four days and then flip it, so that the bottom layer becomes the top. *Do this to ensure the compost stays aerated. Also flip on days 7, 11, and 18. After day 18, the compost will be ready for use as a fertilizer and soil amendment..
Here is a great video on vegetable composting, by expert gardener Eliot Coleman.