While the general rule with houseplants is to not fuss with them too much, occasionally washing their leaves is a really good idea. That's because a thin layer of dust can hinder the photosynthesis process, impeding plants' ability to grow.
To clean your heartier, bigger houseplants, occasionally crowd them into your bathtub and give them a nice, gentle shower. Let them sit in the tub until they dry out somewhat, and then return them to their spots in your home. For smaller, more delicate plants, use a microfiber cloth and a spray bottle filled with water to mist, and very gently wipe, the leaves.
Source: Flickr User ndrwfgg