In a sense all writing style is subjective, since all writers select a particular emphasis for a given set of facts. An article about climate change, for example, can take particular facts about the phenomenon and fashion either a pro or con argument, depending on the writer's approach; articles can reflect opposing viewpoints using the same facts. You must read with a discerning eye to recognize a writer's subjectivity, and how much it may influence that writer's supposedly objective viewpoint.
True objectivity occurs when a writer provides accountability. Consider, for example, a lesson plan written for current education; it must be specific and measurable in its results. The lesson is objective -- and has an objective -- because it is accountable. Academic writing also requires objectivity: The emphasis is on the information the author passes on, rather than opinion or personality. The objective writer will avoid the personal pronoun, and leave out phrases such as "in my opinion," "I think" and "I believe," confining himself to facts rather than his interpretation of those facts.
Most professional writing, including journalism, is objective. Business and technical styles of writing demand research, formal tone, extensive documentation and clear, concise language. Objective writing is free of slang and idiomatic expressions and does not manipulate facts or offer interpretations. Harvard's Nieman Foundation, excerpting Alex S. Jones' "Losing the News," defines journalistic objectivity as recognizing a reporter's bias -- which is inevitable -- but also requiring that the bias stand up to evidence and results. In other words, objective writing style produces results that can be measured, just as in science.
Subjective writing, in contrast, focuses on the writer's experience, personality and opinions. The personal pronoun is evident throughout; phrases such as "I think" and "in my opinion" should be used to distinguish the author's subjective point of view from the facts. Subjective writing exists most vividly in Internet blogs, which feature unlimited subject matter and diverse opinions. Subjective writing, a freer and far less restrained writing style, provides authors with a pressure valve. Even CEOs, whose entire day is spent in writing objective, business-style reports, unwind by writing subjective blogs at day's end.