Light is the food of plants enabling photosynthesis. This process in presence of light, converts water and carbon dioxide into sugars and oxygen.
As a very general rule flowering plants and colorful foliage plants need direct sun, ornamental foliage plants don't need direct sun and will survive in less light and cacti and succulents need lots of sunlight.
Low light indicators are pale leaves, slow, weak growth of stems, leaves drying and dropping, etc. Brown burn marks on exposed leaves, shrivelled dry leaves, indicates too much light.
Water requirements of plants should be fulfilled by regular and appropriate watering. Watering of potted plants should be just enough to wet the complete potting medium. Excess water draining from the pot should not be allowed to collect below the pot as excess water can rot the roots. Humidity of surrounding air also affects the health of plants.
Few methods to increase humidity around house plants are misting (spraying. The benefits of misting are that it cools the plants down in the hot weather, provides humidity to leaves in dry conditions and cleans the leaves.