Making compost is the single most important step you can take toward guaranteeing a healthy garden. Used for thousands of years, it's become synonymous with good land stewardship, and its benefits are legion: It provides nutrients (and changes those already in the soil into forms plants can use), builds better soil texture, helps bring pH levels into the neutral range, promotes good drainage as well as water retention by opening up heavy soils and binding loose ones, darkens most soils to allow better heat absorption, attracts earthworms, helps plants produce their own growth stimulators, fixes heavy metals and other toxins, keeps water-soluble nutrients from leaching away, allows plants to choose their own nutrition based on individual needs, and much more.
Whew! All that, and it's free, too.
For your own source of this magic soil amendment, pick a site near the garden, under a deciduous shade tree if possible (it will provide shelter from the elements and contribute leaves), and with easy access to vehicles if you'll be importing some ingredients.
Though freestanding piles work fine, a bin or enclosure saves time in shaping and keeps the heap neat enough to buffer the possible objections of neighbors. Whichever you choose, be sure the mass measures at least 3' x 3' x 3' to ensure generation of the heat needed to break down ingredients and destroy weed seeds.
A creative scrounger can use boards, poles, wire fencing, old pallets, hay bales, snow fencing or concrete blocks to create bins. At the other end of things are commercial composters sold through garden supply catalogs. Somewhere in between lies the bin built mainly from purchased materials. Choose whatever best fits your abilities, your pocketbook and the tolerance of your neighbors.
You may have heard that everything but the kitchen sink will disappear neatly into the workings of a compost pile. Well, it isn't so. For example, don't add pet feces, large amounts of grease, or fat, coal, coal ashes, barbecue briquettes, synthetics like plastic and polyester, floor sweepings (in some homes these can contain up to 500 parts per million of lead), food preserved with BHT (even small amounts can alter plant growth), sludge (it can contain concentrations of heavy metals), diseased plant material (burn it first, then add the ashes), and overly bulky or hard materials (bones, oyster shells, nut hulls, thick stalks or twigs) unless they're first pulverized.
What you will need to produce a clean-smelling, effective pile are the following: mass (at least a cubic yard), moisture (the heap should be neither soggy nor dry—just damp), air, beneficial microorganisms (found in garden soils or previously made compost), materials that supply nitrogen (all manures and urines, kitchen scraps and green plant residue, as well as blood, bone, cottonseed, hoof, horn and alfalfa meals) and materials that supply carbon (such dried plant matter as straw, hay and dried leaves, grass or weeds).
There are thousands of different recipes for making compost. Here's one that's fairly basic: 1) Lay down bulky material onto bare soil. 2) Fork on a layer of carbonaceous material from four to eight inches thick. 3) Add a layer of nitrogenous matter two to four inches thick. Fluff all material as you go. 4) Repeat steps 2 and 3 (adding sprinklings of soil and water as needed) until the pile is the desired height. 5) Cover with a layer of soil, sod, or stalks or with a waterproof tarp if rain protection is needed. Run-off will leach out valuable nutrients. 6) Turn the pile once or twice at six- to eight-week intervals.
The textbook ratio is 25 parts carbon for every one part nitrogen, but it's easier just to make the carbon layer larger than the nitrogen layer and experiment until you find the proportions that work best for you.
Within four to five days the pile should shrink in size and the interior should become hot (around 140°F). If it doesn't, check the steps above to be sure you've not missed anything. If you notice a strong ammonia odor, there's too much nitrogen. The pile may still break down, but what you smell is nitrogen lost. To correct this, turn the heap, and add more carbonaceous material.