Place your Calathea in a room that gets a medium amount of natural light. Overly bright, sunny windows should be avoided or her vibrant leaves will start to fade. Rotate the plant occasionally to encourage even growth.
Water when the top 1-2 inches of soil is dry. When watering, water the plant moderately and slowly from above, allowing water to soak through to the roots, then tip out any excess water. Be sure to avoid soggy soil. Mist the leaves occasionally and clean them by wiping them down with a damp cloth.