This amount possibly will depend on the type of plant that you have, your location, the plants age and also the type and size of the pot. Constant soil conditions come into play as some soil holds more water than others. You can get more information here http://www.gardeningknowhow.com/indoor/how-to-water-a-plant.htm.
It depends on the kind of plant but generally speaking you should water a plant every other day, or daily if it is especially hot. You want to make sure the water pressure isn't too high and the water sinks into the soil, you don't want to just blast it with water and flood the plant.
It depends on the plant and if it is inside or outside. I find that for onside plants once a week is good. For outside plants I give them a small amount of water daily when it's hot and every couple of days otherwise.