Once they mature,I water till it drains down from the pot.Depends on the strain,but normaly thats when the roots start to grow the fastest.Whatever size your pot is,put that much water in it.You can get fancy & use a scale & moisture meter.But I usualy just pick the pots up everyday after I water & stick my middle finger in the soil.If I feel no moisture halfway up,I water 30-40% of what the pot holds.Or ill water when the pot is about half or less then half the weight of the pot when I first watered.As they get older they will take water faster & need watered more often.And when you need to flush,example:3 gallon pot,you need to pour 9 gallons for a flush.Flushing is,pouring 3 times amount of what the pot holds.
Temps & humidity are also important role with watering.