You will need a strong background in science: you will be studying for a medical degree, and the courses will include anatomy, physiology, psychology, and specific courses about the internal workings of the human body. You will need to learn techniques for diagnosing various diseases, and what certain symptoms mean. You will need to know how to do medical research, so that you can keep up with new findings that may be useful to your area of expertise. You will need to project a confident but calming manner, so that you can put a patient at ease (many patients are scared when they see a doctor). You will need to listen carefully to the patient, so that you can understand his or her symptoms: this will be necessary in order to diagnose, or to identify possible reasons why the patient is not feeling well.
Sometimes, a good doctor is like a detective-- gathering information, knowing what tests to order, doing research, and figuring out the problem. You will also need to possess manual dexterity, since you may be performing surgery or handling medical equipment or doing a physical exam. Some doctors are specialists, and they must acquire a thorough knowledge of the particular area in which they want to practice: gynecology, oncology, internal medicine, surgery, etc. Above all, a doctor must have a love of the medical field and a dedication to helping patients.