Wash a shovel and a large container with soapy water. Rinse everything off with one part bleach mixed with nine parts water. This disinfects the tools so any plant disease infection does not spread to the soil.
Place one part of potting or sterilized soil in the large container. Do not use soil directly from the garden since it may contain plant disease and lots of weed seeds.
Mix in one part sand, perlite, vermiculite or a mixture of these ingredients in the large container. This ingredient keeps the soil light, prevents compaction and improves water drainage.
Add one part of organic material, which includes compost, peat moss or well-rotted manure. Organic material fluffs up the soil, provides nutrients for the plants and increases the water holding property of the soil mixture.
Mix in 1/2 cup of 5-10-5 slow-release fertilizer for every 8 gallons of soil. The fertilizer gives seeds and transplants a boost to begin growing strongly after planting. Fill your container with soil.