Watch the light before moving anything
Spend a few minutes noticing where the brighter and darker areas meet. A curtain, a wall or the distance from a window can change the mood of a portrait. You do not need to turn the whole room into a set to find one useful corner.
Make one change at a time
Move the subject a little, turn towards or away from the window, then look again. Small changes are easier to understand than changing the whole arrangement. Notice the background as well as the face or object you are photographing.
Keep something of the room
A wider photograph can preserve the feeling of home: a favourite chair, the edge of a table or a well-used blanket. Let a few ordinary details stay. They may be what makes the picture feel personal years later.