Because in radiosity light bounces around from every surface you must not forget to always use a complete room. So place a large white square behind the camera (reflecting some light back in from that direction.

In an indoor studio setting, don't use sunlight, use a 3 point lighting for your main subject and add fill lights to light the rest (use at least 2 for the background and at least 1 for each additional subject, extra fill lights may be required).

In an indoor natural setting, use sunlight as the main light, add a key light over your shoulder directed to the main subject. Extra lights should only be used for dark corners (and should make sense, so a light fixture should be expected to throw this light). The human eye puts the focus on the main subject, the rest becomes a blur. In pictures we have to provide enough light and detail in the entire picture but we simulate the focus by providing a bit of extra light on the main subject.