Getting tomato plants to produce plump healthy tomatoes is slightly complicated. When you get home with a tall leafy tomato plant it seems like it should just be placed into a container or the ground like any other vegetable but that approach is not likely to yield great tomatoes. These are growing tips from the Oliver Garden:
Purchase plants that will bear fruit at different times so you can harvest tomatoes from July through early September.
Remove the bottom half of the leaves and bury the stem up to that 'new' bottom leaf. Tomatoes develop roots along that long stem under the dirt. This makes for a stronger plant and more roots mean more fruit.
a minimum of ten hours of sun is best and Space the plants so there is plenty of air circulation.
Use Tomato Tone (an excellent organic fertilizer) per the directions. Bonus: It comes in a bag which will last a couple summers and It's good for any vegetable.
Stake or cage each plant, actually do both for best results. healthy plants get so heavy with produce they just topple over.
As the plants reach roughly 3 ft. tall, clip off the bottom few leaves to prevent fungus problems from developing.
How tomato plants are watered is important. The goal is to keep them watered on a consistent basis to prevent blossom rot. water deeply - a good soaking - and then let them dry out some before watering again. If they are not getting much rain water, a watering schedule of every 2 days works well. irregular watering will reduce the size of the tomatoes and quantity. and....if they have a period of time where they are too dry for too long they will die off and won't recover.
Water the soil, not the leaves (because who needs vegetable fungus issues when it gets hot outside). If the leaves are looking yellow and crispy, the plant is not getting enough water. If the leaves are looking yellow and droopy, the plant is getting too much water.
if things don't go well one year find a great farmer's market. then try again the next summer. don't give up, it gets easier each year.