Houseplant care advice often focuses heavily on watering schedules, but light conditions and a genuine, common misunderstanding about watering are bigger factors in most houseplant deaths than following an exact watering calendar.
Overwatering is the more common killer, not underwatering
Many new plant owners worry primarily about forgetting to water, but overwatering is generally considered the more common cause of houseplant death — excess water in the soil displaces oxygen around the roots, and roots sitting in consistently soggy soil can develop root rot, a condition that's often fatal and can be difficult to reverse once established. Checking actual soil moisture (by feel, a couple of inches down, rather than by a fixed calendar schedule) before watering, and allowing soil to dry to an appropriate degree between waterings for the specific plant, addresses the more common real risk better than a rigid watering schedule that doesn't account for actual soil condition, temperature, and humidity variation.
Light level matters more than most other care factors combined
Matching a plant's actual light requirement (low, medium, or bright indirect light, or direct sun, depending on the species) to where it's actually placed in a home has a bigger overall effect on plant health than most other care variables — a plant placed in insufficient light for its needs will generally struggle and decline regardless of how well other care factors like watering and fertilizing are managed. Checking a specific plant's actual light requirement against real available light in an intended location, rather than assuming any spot with "some light" is adequate, is worth doing before purchase, not after a plant has already started declining.
Drainage holes are a real requirement, not a preference
Pots without drainage holes make it much harder to avoid overwatering, since excess water has nowhere to go and simply pools at the bottom around the roots — a decorative pot without drainage can still be used as an outer cover, with the actual plant kept in a properly draining inner pot (a technique often called "pot within a pot"), rather than planting directly into a pot with no drainage at all.
Humidity and temperature preferences vary significantly by plant origin
Many popular houseplants originate from tropical environments and prefer higher humidity than a typical indoor home environment naturally provides, particularly in winter with heating systems running — plants struggling despite otherwise correct light and watering are sometimes suffering from inadequate humidity specifically, which can be addressed with grouping plants together, a humidity tray, or a humidifier for plants with genuinely high humidity needs. Checking a specific plant's actual origin and humidity preference explains some care struggles that watering and light adjustments alone don't resolve.
The one thing people forget
Research a plant's toxicity to pets and children before bringing it into a home with either, since a genuinely large number of common, attractive houseplants are toxic if chewed or ingested, ranging from mild irritation to more serious reactions depending on the specific plant and amount ingested. This is worth checking specifically for each plant considered, rather than assuming a plant sold in a regular garden center or home store is automatically safe around pets and children.