With the recent rains and cooler weather, you shouldn't have to water much. I suggest you give them a gentle watering when you plant the seeds, and then check daily for several days to see if the soil is drying out. You may want to water gently every day or two for a week, until the plants start putting down roots. After that you can judge from the amount of rain we get. If there's no rain you may want to water gently once a week. I understand that carrots like good drainage, as they don't want to get too wet.