Tomatoes thrive in well-draining, fertile soil with a pH between 6.5 and 7.0. A soil test in the fall can determine the garden soil's pH; after obtaining the results, amend the soil accordingly to bring it within the ideal pH range. Before starting tomatoes, work a 2-inch layer of organic matter such as compost, peat moss or well-rotted manure into the soil. In addition, till a 6-24-24 or an 8-32-16 fertilizer into the top 6 inches of soil, using a rate of 1 pound per 100 square feet.
Transplant tomatoes in a sunny, wind-free area of the garden after the last spring frost when the temperatures are 65 degrees Fahrenheit during the day and 50 degrees F at night. Space tomatoes at least 2 feet apart to promote air circulation; if you're growing large vine tomatoes, space them 3 feet apart. Space the rows at least 4 feet apart. For support, place 6-foot-long stakes about 4 inches from the seedlings. Alternatively, use tomato cages to keep the fruit off the ground.
Tomato plants need consistent moisture during the growing season to establish strong roots and to prevent problems such as fruit cracking and blossom end rot. Provide them with up to two inches of water per week. Water the soil to a depth of 8 to 10 inches early in the morning, and avoid getting water on the plant. Adjust the watering frequency after rainfall or during dry, hot periods. Spread a 2-inch layer of organic mulch, such as seed-free straw or dried grass clippings, around the plants to promote soil-moisture retention and to combat weeds.
Rather than fertilizing tomatoes one time, provide these heavy feeders with regular nutrients as they develop. Side-dress with a 5-10-10 fertilizer every three weeks, starting when the tomatoes are the size of golf balls. Dig a 1-inch-deep, circular trench around the stem of each plant. Keep a 5-inch distance between the trench and the stem. Sprinkle 1 1/2 tablespoons of the fertilizer in the trench, and backfill it. Water the trench to bring the nutrients to the plant roots.