Keep the compost moist during the warmer months, reducing the frequency and volume of watering in the winter. Let the moth orchid stand in a tray of water to soak up for an hour or two if quite dry, rather than watering little and often in soft, tepid water.
They love humidity and prefer even temperatures, so a bright kitchen or bathroom would be ideal, and mist the leaves with water occasionally, especially if they are in a heated room. Don't worry if the roots grow outside the pot and repot the orchid when the growth starts to suffer. Only one or two flower spikes are produced during the year. To encourage a second flush of flowers, trim back the stem to just above the first node immediately after flowering.