Portals

In addition to the answers regarding samples, you could use portals to decrease your render time, allowing more samples for the same amount of render time. (Sometimes, in some cases; portals get rid of a bit of noise as well)

Light Portals

In addition to the answers regarding samples, you could use portals to decrease your render time, allowing more samples for the same amount of render time. (Sometimes, portals get rid of a bit of noise as well)

Note: Portals don't change the look of your render, they get rid of the non-visible light rays outside of your room.