Do a quick review before you buy houseplants; Look at the spaces where you'd like to have plants – note the amount of room, light and temperature levels and location of any heating or AC vents (most plant don't drying air blown right at them indoors). Consider your desired look and feel for the space, just as you would with furniture or decor.
Too much light will fry a plant, too little and it will grow leggy and straggly. Many plants will grow in a range of light, say medium to bright, rather just one strict level of intensity - so you'll have a little flexibility.
Common light level terms and what they mean for plant placement:
LOW: morning sun near an east facing window, directly in a north facing window, or 6 feet away from a bright window.
MEDIUM: 3 to 5 feet from a window that provides several hours of sun
HIGH/BRIGHT: Within 2 feet of a full sun exposed window (usually south facing*)
You may see the following instead of or along with Bright:
DIRECT: no shading and within 2 feet of the light
INDIRECT/DIFFUSED: 3 to 5 feet from a window that provides several hours of sun, or closer to a bright source with a sheer curtain between.
*In the Northern hemisphere, rooms with windows on the East and South will get the most light.
Succulents/cacti and orchids should be potted in mixes specifically labeled for them, for all others use potting mix - not outdoor soil (potting mix is lighter and free of bugs and pathogens).
Pots really do play a big part in houseplant health due to their role in soil moisture;
Size: A too small pot won't hold enough soil and thus, available water, leaving the plant thirsty or you wore out from frequent watering. One that is too large will hold excess water and not enough air, resulting in the suffocation of plant roots.
Most plants do well in a pot that would leave a 1-2" space between the outermost roots and the pot wall. Some plants like to be a bit cozier, but once the roots are circling the inside edges of the pot, it's time to take action. You can repot - trimming back the roots to once again be a good fit to the current pot and balancing this by removing a bit of the top growth also. If you have space, you can Pot Up – moving the plant, untrimmed, into a pot several inches larger in diameter than its current one. Be sure to use fresh potting mix in either case.
Glazed or Not: glazed pots retain more moisture than unglazed, which can be especially helpful in a heated winter environment, or bright light, to reduce watering frequency. Unglazed pots (think terra cotta), however, are a great choice for cacti, succulents and other plants that like to dry out a bit.
Drainage: a lack of drainage will lead to suffocation or rotting of roots. If a pot has a drainage hole through the bottom, a saucer should be used beneath it. Some pots come with a perforated false bottom on the inside that leaves room for drainage beneath it and eliminates the need for a saucer
Your plant should come with a tag that gives a general watering guideline, such as; Keep soil consistently moist or allow soil to dry before watering. How frequently you water will depend on what it takes to keep the soil in that recommended condition - with most plants being in the range of every 7 to 10 days. Note that consistently moist does not mean soaking wet. For those that should dry out before watering, most do best if you take this to be the first top inch of soil – not so dry that all the soil is pulling away from the pot edges.
Take a moisture-reading before and after watering; you can easily check for moisture by sticking your finger into the soil. A dried out plant will also feel much lighter than a well-watered one if you pick up the pot. Actually looking at the potting soil also helps. Do not rely on the often given tip to"…water until it runs freely from the bottom..." as water will flow straight through soil that is too dry and fill the saucer instantly. Think of a dried up sponge that initially refuses to take on water – you have to soak it well to get it to begin taking in water once again. Once you're sure the soil has taken in water, pour out any excess from the saucer.
Because houseplants must survive in a limited bit of “earth", not replenished by Mother Nature, they need an assist when it comes to nutrients. The most popular choice for feeding/fertilizing houseplants is water-soluble plant food (a concentrated powder or liquid that you dissolve in water) as you can complete feeding and watering at the same time. The plant food package will advise on the ratio of concentrate to water and frequency of application for the particular brand. Once weekly during active growth is typical, with the active growth period for the average houseplant matching the seasons outside. During the “off season" feeding is generally reduced to once per month. Specialized foods are generally best for African Violets and Orchids.
Finished blooms and dried up leaves can be trimmed off, right next to the plant stem, with no harm to the plants. If your plant has a long bloom stalk, such as an orchid; remove finished flowers, but leave the stalk, as it will often produce more flower buds over several weeks. Once the stalk begins to brown, feel free to trim it away.