Since most of the roots of interior plants are in the lower two-thirds of the pot, this is the area you have to water. The rule to follow is to water the pot until water runs out of the bottom. How much water should run out? About one-tenth the amount of water you applied. Watering this way serves two purposes. First, it guarantees that the lower two-thirds of the pot was properly watered. Second, it helps to flush out fertilizer residue (excessive salts).
The pot should not be permitted to sit in the water that drains into the saucer below. To do so would cause a re-uptake of the fertilizer residue that should be flushed from the soil. After permitting the pot to drain for an hour or so, remove all excess water in the drainage saucer.
When a plant becomes very dry, sometimes the soil will pull away from the sides of the pot. Watering very dry plants requires special attention. In such a case, you should water the plant as described above. Wait a few minutes and remove excess water from the saucer. Re-water the plant. Failure to remove ex cess water from the saucer may result in an overflow with the second watering. This second watering allows the water to penetrate the soil. Sometimes, a third watering may be required.