There has been a lot of debate about how to water a tomato plant. Too much and you’ll get fewer tomatoes, not enough and they will crack. The quality of the fruit is defiantly on the line. Here is a system I developed for beginners, which also works for old-timers like myself. First you need to understand the crop. It’s okay to let them dry out between watering when they’re young -- to the point where they’re just about to wilt from lack of water. This will produce flower production. They think they’re dying and when they do get watered they go into full flower production. Their whole job is to produce seed for the next generation, so they think “Okay, this is it, the only water I'm going to get” and the kick it into gear. So, don't over-water in the beginning.
When fruit starts to form you need to count how many days it takes for the plant to start to wilt. Lets say it’s 5 days. In that case, your watering schedule will be every 4 days. This will change with weather and outside temperatures, so adjust accordingly. This way they get just enough with out drying out completely when in fruit production. When fruiting, don't let them dry out because this is why your tomatoes crack. They store water in their fruit for drought, and they will take this water if needed. The tomato shrinks, and then when you water they fill their storage container (tomato) and they burst. There really is an art to watering tomatoes!