My tomato plants have blooms, yet they do not yield fruit.
Not enought sun. Soil conditions could be poor. You can add epsom salts and bone meal to the ground to boost nutrients. This really should be done 2 weeks before planting, but you can add them around the area. You also should mulch the area around the tomatoes with peat moss and vermiculite You should also begin training your palnts by staking them. I read in the farmers almanac (2009 issue) that when 6 leaves grow on the top, you should cut the middle top off. Also, remove any sucker branches that grow on the side as this makes it hard for the plant to produce the fruit.