What are the common causes of paint cracking and how can it be prevented or fixed?

Common causes of paint cracking include applying paint too thickly, using low-quality paint, not allowing sufficient drying time between coats, and painting over a dirty or damp surface. To prevent paint cracking, ensure proper surface preparation, use high-quality paint, apply thin coats, and allow adequate drying time between coats. If paint cracking occurs, it can be fixed by sanding down the affected area, applying a primer, and repainting with thin, even coats.