Do tonal drawing of your interior from last week.
Break down the layers into:
0.Tone back the canvas to 30%- 50%
Remember to pay attention to first, where the shadows are and aren't. Secondly what the edges are like. ie, Hard or soft.
where 2 or more planes meet, and holes or pockets where light canno't reach
3. Local Values
the dark or light of an object, eg light wood, dark iron, etc
Areas where light or glints of light appear