What are the common causes of cracks in walls and ceilings, and how can they be effectively repaired?

Common causes of cracks in walls and ceilings include settling of the foundation, temperature changes, moisture, and structural issues. To effectively repair these cracks, one can use materials like spackling compound or joint compound to fill in the cracks, followed by sanding and painting to blend the repair with the surrounding surface. For more severe cracks, it may be necessary to consult a professional for a more extensive repair.