Tomato plants need a bit of help to reach their full fruit-production potential. The best way to grow large quantities of tomatoes is to keep on top of pruning. Pruning the plant allows it to focus all of its energy on developing tomatoes, as opposed to supporting non-fruit-bearing branches. Though, depending on conditions, an unpruned plant might offer more fruit, it's also far more likely to develop fruit rots and leaf issues because of trapped moisture. Pruning the plant ensures that it produces healthy tomatoes steadily throughout the season.
Start pruning the tomato plant as soon as the first flower cluster develops. Use a pair of garden shears to snip off all leaves and sideshoots below the flower cluster on the main stem. They will not produce any fruit and will burn up the plant's resources.
Support the plant properly by staking it. Drive a stake into the ground about 4 inches from the seedling immediately after planting. When the first flower cluster develops, tie the main stem to the support with soft strips of cloth. Loop a piece of cloth around the area of the plant that's about a foot from the top of the vine. Cross the tails to make a figure-8 pattern, then tie the tails behind the stake. Make a similar figure-8 wrap directly above the first flower cluster to support the fruit-bearing branch.
Loop cloth ties above each flower cluster at they emerge, crossing them over to make a figure-8 and tying them behind the stake. This will train the stem upward, allowing its leaves to drink in as much sun as possible.
Pinch off suckers as soon as they appear. Suckers are tiny leaves that sprout between the main stem and its offshoot, fruit-producing branches. Simply grip the sucker at its base, where it meets the main stem, between your thumb and index finger and pop it off of the vine.
Top the tomato plant about 30 days before the first frost in the fall. Cut off the top off the main stem, just above the uppermost cluster of developing fruit, and use a pair of gardening shears to trim away any developing offshoots with no flowers. This will allow the tomato plant to channel its energy into making sure the developing tomatoes are plump and sweet, instead of producing a scant final crop of hard, mealy fruit that is inedible.