Just like most tropical houseplants, grow dieffenbachia in a relatively warm, humid spot with plenty of light. If the leaves develop brown tips or edges, the air may be too dry. Remedy this by relocating your dieffenbachia to a well-lit bathroom (or other humid spot), grouping it with other houseplants (which release moisture into the air as they breathe), or set it on a pebble-filled tray of water (so the bottom of the pot rests on the pebbles, above the water to keep the roots from rotting). Dieffenbachia plants like regular watering, but they don't ever want the soil to be wet or soggy for extended periods. Because more indoor plants die from over watering than under watering every year, it's best to keep dieffenbachia on the dry side if you're in doubt about whether to water it. Fertilizing dieffenbachia encourages it to grow more and faster. At minimum, it's best to fertilize dieffenbachia once or twice a year, but you can do so more often if you wish using any general-purpose fertilizer.