Before you dive into growing tomatoes, you have to think about a few issues.
Growing tomatoes requires these basics: soil, water, sun, and a little tending of the garden on your part. These components will come together in a specific location in your yard. This location is of prime importance!
Do you have a spot that gets at least 6 hours a day of direct sun? Is this spot a convenient place for a garden? Can you protect tomatoes there from kids, animals, and splashed chlorine? Is the soil in that location suitable for gardening? Will you be able to water that location?
Location, location, location.
If you don't have a good place to put tomatoes in the ground, maybe you have to consider container gardening. If the only suitable spot that gets full sun is on your deck, it's time to think about growing tomatoes in pots. Since container gardening is not the focus of this website, I'm providing the following links that have a lot of information on container gardening:
Tomatoes, like most other vegetables like a rich, loose soil high in organic matter that drains well. What does this mean to someone who has not gardened before?
For starters, if your soil is too sandy, that's not good. If it's too high in clay, that's not good. If it has no nutrients, that's not good. If it's compacted down and hard as a rock, that's not good!
Good soil is loose, dark, drains well, and is full of nutrients. The best way to insure good soil is to dig it up to loosen it up, turn it over, and add compost to it. If your soil is not good you may want to consider raised beds
where you can buy topsoil and compost and really control your growing medium. If you see worms in your garden soil that's a good sign. Worm droppings are full of nutrients for your tomatoes, worms loosen up your soil so that oxygen and water can get down to the plant roots, and the presence of worms indicates your little ecosystem underground is as it should be.
As a general rule of thumb, tomatoes require a good watering twice a week. Of course, this will vary depending on your soil and climate. Sometimes rainfall provides enough water, sometimes not. When you water, make sure that you water heavily enough for the water to travel down to the roots of your plants. It does no good to moisten only the top couple of inches of your soil; you need the water to go down to the roots. If your soil is too compacted, water will have a tough time seeping down far enough, and so will oxygen. You need loose, well-draining soil for healthy plants.