A job title is capitalized when it is associated with a specific individual's name, or in place of the name. For example when writing Professor Holden; "Professor: is capitalized.
Similarly, a job title is capitalized when it follows an individual's name. An example is in the signature line of correspondence: Mel Childs, Elementary Teacher. The only other instance a job title is capitalized is when the title takes the place of an individuals name. In the sentence, "We met with the Archbishop of Canterbury today," Archbishop: is capitalized as the title is used in place of the person's name. When speaking generally; job titles are not capitalized.