The best spot is somewhere in your yard in a location that gets a good number of hours of bright sunshine each day. Plant it in some good quality topsoil; any kind of quality organic compost material can really help too. You won't need to water much if you've had a wet spring and continue to receive rainfall. If the leaves start to wilt, that's the plant letting you know that it's thirsty.
If you don't have a spot to put it in the ground, you can grow it in a pot on your deck or patio or wherever. Just use a fairly large pot, and be sure to have some sort of tomato plant cage for support. You would also probably need to water a tomato plant in a pot every day, as they tend to dry out quickly when not in the ground.