Over watering ranks first in causes of houseplant demise because it causes roots to rot. Most plants are tough so they can recover from under watering with only loss of a few leaves -- unless you wait too long and pass point of no return.
Watering schedules depend on kind of houseplant, its size, container, and environment. No two plants have same water requirements, so you'll need to know what your particular plant(s) require.
Generally, it's best to water during morning hours. Most flowering plants require more water than their non-flowering counterparts. Since needs of individual plants vary greatly, you should research your houseplant's requirements.
Test dryness of soil by probing top inch with your finger. Tapping side of post also indicates degree of wetness. If tap sounds hollow, plant needs water. If it sounds solid, wait a day or two to water. If a plant begins to wilt and its soil looks dry and cracked, it needs water immediately.
For plants that require moderate watering, allow 1/2 to 1-inch of soil to dry out before re-watering. If a plant needs light watering, let two-thirds of soil dry out. For plants that need heavy watering, surface should always be moist.