From everything i read 1 inch a week should be sufficient . You have to treat a tomato plant like your child, but the rewards are very good if you pay attention to how it reacts each day to conditions. If the leaves begin to shrivel you should give it a light watering and it will recover quickly. This seems to encourage the root system to grow more deeply, (as does the initial planting up to the first leaf area when first planted ), and discourages any type of leaf funguses and bottom rot issues.
Steady and equal watering techniques help to relieve stress. In NC, we always need more good compost to balance water and ph and soil softness, so you cannot overdo the addition of a good nature compost material worked in to the soil. I have a few issues with too much water I think, but its not well drained because of the hardness and clay composition of the ground, so always dig as deep as you can and add good cow manure or anything to break up the hardness will help and let the roots draw in the nutrients more easily. Stick to root watering only after blooms form to keep leaves dry to discourage fungus and leaf issues, and watch for early signs of any humidity issues such as leaf blight or bottom rot.