Don’t over water. Let the soil dry out a little in between waterings. Each plant will have different requirements for soil and amount of water needed, so make sure that you take that into consideration.
They need a rest. Plants do a lot of growing in the warmer seasons so they would need less food and water in the winter or off season along with less heat. Most plants have indoor growing instructions and outdoor instructions, sometimes they are different.
Give them extra humidity. Most plants don’t like desert dry air. You can mist them, keep plants in groups or double pot them to help keep their air environment moist. Also try to keep them away from direct heat sources.
Learn to repot. Once a year or sometimes every other year your house plants will need to be repotted. This gives them fresh soil and some extra growth for their roots. As a general rule only go up 1 pot size and only plant as deep as the plant was in its old pot.
Choose wisely. Do some research on what plants will do well in the rooms of your house and what kind of care you can give.
High light: Jade, Spider Plant, Crown of Thorns, Ficus, Gerbera, Ivy, Banana Tree, Mother in laws tongue (grows anywhere), Wandering Jew
Medium light: Asparagus Fern, Dracaena, Cordyline, Ferns, Schefflera, Pothos, Spathiphyllum, Variegated Syngonium
Low light: Foliage Begonias, Palms, Philodendron, Solid Syngonium
Plants that are the best for improving air quality in the home:
Aloe Vera, Areca Palms, Bamboo (also acts as a natural humidifier), Boston Fern, Ficus Alii, Gerbera Daisy, Peace Lily, English Ivy, Dracaena, Mother in Laws Tongue (or Snake Plant)
Stem cuttings: Choose a sturdy, non flowering section of the stem. Woody varieties generally need some extra help with growing conditions, you should consider using a rooting hormone for these.
Whole leaf plus stalk: Break off a leaf, cut straight across the base edge and dip into a rooting hormone before sticking into dirt.
Whole leaf: Ideal for succulents. Let the leaves dry for a couple days prior to planting. Put a layer of sharp sand over the dirt. Push the ends of large leaves into the soil and for small leaves lightly press them into the soil.
Part leaf: Standard for Begonias, Streptocarpus and Sanservieria. This process is more detailed and specific to the type of plant being cut. I would recommend looking up your specific variety before doing this procedure to get specific cutting angles and sizes.
Too much water vs Not enough water: This is the most common mistake in houseplants. Its critically important to know the differences between over and under watering.First sign of overwatering is that the leaves droop (most people mistake that for a sign of lack of water) then collapse soon follows. Also, yellowing leaves are a sign and you might see a green slime on the top of the soil or on clay pots. When under watering the the leaves will get a shriveled or crunchy feel and turn brown. When the plant doesn’t have enough water the dirt will often dry up and pull away from the pot.
The right light conditions:
High light: Sunny Windows on the south side of the house.
Medium light: Most common and varies depending on variety. Generally means direct light from east and west facing windows or indirect bright light from south facing windows.
Low light: Could be anywhere from from totally shaded windows to rooms that get enough light that you could read a newspaper.
Varies by plant so keep it in mind when trouble shooting.
This is better on a case by case basis, in my opinion. There are a number of bugs and funguses that can hamper the growth of plants. You should treat them at the first sign of a problem. Bring in a sample of the problem and we can help you diagnose the issue and help you find a solution.