Water: Allow the plants to dry between waterings, but not completely. These are more susceptible to root rot, so be very careful never to allow them to sit in standing water.
Nutrients/Fertilizer: A once-a-month with weak solution of balanced fertilizer is usually sufficient.
Light: Dieffenbachia are well in medium light. Any place in your house will do good in a brighter area.
Note: Images are for reference purposes only. Actual product may vary in shape or appearance based on size, Age, Seasons, etc.