Choose a Bright, Airy Spot
Plant tomatoes, leaving room between plants for air to circulate, where they will get at least 10 hours of light in summer.
Rotate the Crop
Alternate your tomato bed between a few spots in the garden to diminish the risk of soil borne diseases such as bacterial spot and early blight.
Pass Up Overgrown Transplants
When buying tomato seedlings, beware of lush green starts with poor root systems. They will languish for weeks before growing.
Bury the Stems
Plant your tomato seedlings up to the first true leaves. New roots will quickly sprout on the stems. More roots mean more fruits.
Water Deeply but Infrequently
Soak your tomato bed once a week, or every five days at the height of summer. Water directly on the soil, not on the leaves.
Pinch the Runts
Prune off these non-fruiting branches. This directs the tomato plant’s energy into growing bigger, better fruit.
Stake them High
Use 6-foot stakes for indeterminate varieties like the ‘Brandywine’ tomato. Put in the stakes when transplanting to avoid damaging roots.
Add Compost and Trim
While the first fruit is ripening, encourage new growth and continued fruit by scratching compost around the stem and trimming some of the upper leaves.
Plant Again
Three weeks after you plant tomatoes in your garden, put in another set so all of your harvest doesn’t come at once.
SOURCE: http://www.organicgardening.com/learn-and-grow/secrets-tomato-growing-success