You need to allow a minimum of 6 hours per day of direct sunshine. When you plant your tomato plants, you should always plant them deeper than they have been growing in their pots. The stem has the ability to sprout roots when it is buried underground which allows the plant to double its root system very quickly which means that it can take up more water and nutrients that it needs. This will also add stability to the plant and makes the stem grow strong. Watering is not nearly as important as you would think.
Tomatoes grow in very dry conditions in many parts of the world without a problem.
Over watering is the number one cause of tomato diseases. It also makes the fruit taste bland and washes away soil nutrients from the roots. Drip systems are very good for tomatoes as they water deeply without wetting the leaves and stems which causes diseases. Let your plant tell you when it is thirsty, the leaves will look like they are starting to wilt. A deep watering will revive them within 10-15 minutes.