My plan for this season is to water deeply in mid afternoon daily. For example, I watered yesterday at around 3 PM. It is just a bit after 3 today, and sun is shining, the temps are in the mid 80s - and the tops of the plants are starting to droop a bit. So after I dash off this blog entry, I am off to pick up the hose and get to work and provide the necessary drink for the plants.
If you have plants growing in good garden soil, daily watering will likely not be necessary due to the far greater water holding capacity of a large garden. Let the plants tell you when they are thirsty - look at them a few times during the day and watch for the wilting tops of the plants.
As far as overwatering - if you are growing in containers using good loose potting mix amended with compost and have drainage holes, it is literally impossible to overwater a tomato. If, however, you are planting in garden dirt that is very rich in clay and the drainage is poor, you can easily suffocate (drown) a plant. In that case, during a season with normal rainfall, weekly may indeed be sufficient.
Off I go to work the driveway with the hose!