If the possible causes of symptoms (presented by the patient) & signs (detected by you) are known then the clinician can easily make a list of differential diagnosis by co-relating all the possible causes. So to become sharp clinically it is essential to learn more and more about etiology of symptoms and signs. Etiology of different systems are-

Etiology of general examination findings
Etiology of Cardiovascular system
Etiology of respiratory system
Etiology of GIT
Etiology of nervous system
Etiology of Genitourinary system
Etiology of acid base and electrolyte disorders
Etiology of nutritional disorders
Etiology of Endocrinology
Etiology of Musculo-skeletal disorder
Etiology of skin diseases
Etiology of STD