QUESTION: How do you encourage tomatoes to fruit?
ANSWER: To encourage tomato plants to fruit, stop providing them with fertilizers that are high in nitrogen, even compost and manure, as nitrogen-rich fertilizer encourages production of foliage and not fruit. Fertilizers with a low first number are fine to give, and even better is a potassium-rich fertilizer like sea kelp.
You can also encourage the plant to fruit by pruning away the suckers that grow from where a branch meets the main stem and also trimming some of the lower leaves, but do not use pruning on determinate tomato varieties. You can also try gently shaking the tomato plant to help distribute the pollen so that the blossoms get pollinated and begin to set fruit.