You should be letting them get all but dry in between waterings. You want your roots to dig and expand searching for water so you end up with more root massYou should place alot of emphasis on root health.
I wouldn't use plain water unless your soil has nutrients in it. If your growing medium has no nutrient in it then I would be feeding with nutrients.
the soil should be pretty dry on top and the pot should feel considerably lighter. If your drainage holes are big enough stick your finger in and feel how dry it is down the bottom
water untill it comes out the holes. Try and moisten all of the soil. Once your plants get big enough and once you get to know them, You will see the Changes they make in between waterings. They will slowly start to sag and droop as the water in the soil runs out and just when that starts, Its time to water