lil' bits of this-n-that: Healthy Indoor Plants

LIGHT

Plants need light to produce their food. But they need the right amount of light depending on the type of plant it is. Most plants come with some form of printed care instructions. Be sure to keep this information with the plant so there is never a question of a plants proper care.

Your plant is getting too much light if the leaves are turning down and may or may not have a bleached out look.

Your plant is suffering from too little light if it slowly loses old leaves, produces even smaller new ones and becomes tall and spindly.

WATERING

Water your plant whenever it is necessary. The soil surrounding your plant should be damp but not wet. Water until you see water coming out of the drainage hole (the one you remembered to make when the plant was first potted) so you know water got to the roots also. You'll want to make sure the drainage hole is not clogged up with roots either.

Feel the soil on top. If it's dry, it probably needs water. This can be misleading too because it could be damp underneath the surface.
Knock on the side of the pot. A dull sound means it's moist, don't water anymore. A hollow sound indicates it's dry and needs to be watered.
The finger test comes highly recommended. Poke your finger about an inch (up to first knuckle) down into the soil. If it feels dry, add water. If it feels damp, hold off for a few days and test again. If it feels wet, it could be over-watered. This can be just as bad for a plant as no water at all.

MORE INFO

The temperature of the water is important. You don't want to shock your plants. A range of 62 to 72 degrees sounds about right.
Use either distilled water or rain water if you can. Softened or hard well water can be hard on plants. Chlorine and fluoride can build up overtime and cause significant problems.
Do not let the plant sit in water. This will keep the soil in the pot too wet.
Some plants require a dry time in between being watered. That's why it is so important to consult the care instructions for each individual plant.
Some plants that wilt between watering will recover well after watering but others that wilt will not recover. Wilting is very stressful for the plant. Don't take a chance on losing your plant.