Leaf color is a good indicator of proper amounts of light. Dark green leaves may indicated insufficient light. A yellow leaf is receiving too much sun exposure. Provide enough light to provide a light greenish color with firm leaves. Do not let the psuedobulbs become shrivelled.
Humidity is important.
Plastic pots retain more moisture while clay pots will require a little more water. It is important to check your plant before watering and remember to let the medium dry out between waterings. Cattleyas can tolerate short periods of drought and do best with a watering schedule that allows them to dry before watering. Cattleyas generally like temperatures 75-85 F range, but can tolerate higher temperatures with good air movement. This is considered temperatures intermediate to warm.