Many prospective martial arts students are very quick to sign up at the closest, least expensive, or more popular school in their area. However, finding the right Martial Art instructor can be difficult.
Realize that expertise is not easily reached and anyone who promises otherwise is lying.
The Sensei (instructor) himself should be neat and clean. His attitude should be friendly, professional, and respectful, not only towards you but towards his students, the other instructors, and other schools and styles.
Ask him first about his credentials. When did he begin studying? Who was his instructor? When did he reach Black belt? How long has he taught? Did he create his style or is he part of a well established system? What association does he belong to? Does he have a teaching certificate from his association? Who is its head and what are his credentials? Does the school compete in open competition? If it never does, it may be hiding its frailties.