Don’t overwater (the commonest cause of houseplant death). It kills the roots, making plants collapse. Always let the surface of the compost dry out before watering and allow excess to drain away. Or water from below by standing plants in a bowl of water. Reduce \ watering to a minimum during winter. Mist regularly in dry conditions such as in centrally heated rooms.
Provide stable conditions away from draughts. If necessary, move plants away from open fires, or from cold windows at night.
Light and air
Bright filtered light, not scorching direct sunlight, is ideal. Foliage plants are best suited to low light levels.
Use a shop-bought liquid feed from spring through to autumn, while plants are growing actively.