Start a compost heap. Layer "green" materials like non-animal kitchen waste, grass cuttings and green yard debris with "brown" materials like dried leaves, straw or un-dyed paper products. Turn the pile once a month with a digging fork and keep it moist. After a year you should be rewarded with a rich, sweet-smelling soil that is rich in nutrients and beneficial microbes.
Build good soil. Conventional gardening with synthetic fertilizers aims to feed plants. In organic gardening, your goal is to feed the soil so the soil feeds the plants. Nourish microbiotic life in your soil with organic amendments like compost, aged manure and yard debris like leaves and grass cuttings. Healthy microbes in the soil eat harmful bacteria and fungi, and they break down nutrients into particles plants can take up through their roots.
Work the soil by hand. Tillers chop up worms and upset the balance of microbiotic life in the soil. A tiller can also compact the soil, which interferes with water and air circulation. Mechanical tilling might be necessary for a very large space, but till a small garden with a shovel, rake and digging fork.
Spread at least 2 inches of organic amendments on the soil surface and work them in. Dig the amendments at least 6 inches into the soil, and use a digging fork or a rake to break up chunks of dirt to pieces no larger than a pea. This approach is very work-intensive the first time, but in future seasons it will be much easier to prepare the garden. Weeds in loose soil are easier to pull out, and water and air circulate more effectively.
Plant organic seeds and seedlings. Conventionally-grown seeds and starts can contain harmful chemical residues that can get in your soil. Make sure the plants you choose are suited to your region and climate. If you have the wrong kinds of plants, they will be weak and more susceptible to pests and disease.
Keep on top of the weeds. Weeds are a fact of life in organic gardening. Get them out while they're small, and take care to pull up the entire taproots. Burn weeds or throw them away with the garbage instead of composting them, because many seeds can survive in the compost.
Water your garden well. Watering in the morning is best because the water has a chance to get to the roots before it evaporates in heat and wind. Water your plants right at the roots instead of from overhead. This saves water and it helps prevent weeds, which will grow anywhere the soil is wet. Wet plants are also more prone to fungus and disease.
Mix up your plants. There's no rule that plants have to be in neat rows of all the same crop. Include flowers and herbs in your vegetable garden to attract beneficial insects like bees and butterflies. Marigolds keep away many types of insects and beetles, as do strong-smelling plants like garlic, thyme and basil.
Remove pests by hand as much as possible. Check your plants every few days for signs of pest infestation. Look carefully under leaves and along stalks. If you find something eating your plant, squish it or throw it away. If there are more pests than you can manage this way, consider using an organic insecticide like diatomaceous earth or a vegetable-based spray.
Rotate crops from year to year. If you keep putting your crops in the same place, diseases and insect eggs from the previous year are more likely to attack.