A good idea to figure out when to water your plants, water them plenty so the soil is well saturated (don't drown them though), pick up the pot, get a feel of it's weight.
When the pot dries up from being absorbed by the plant, it will become lighter.
Now you can tell when your plants need a watering by the weight of the pot.
It's also a good idea to let the plants absorb all of the moisture in the soil by not watering as often. In nature plants don't have a steady supply of water at all times and the times they get water are not on a schedule.