Identify someone by the full name first, and then only by last name in the rest of the article.
Only refer to titles when they are titles of distinction (eg. Dr., Sensei, Grand Wizard and so on). Mr. or Mrs. is unnecessary. Gender should be identified through speech.
In the case of two individuals referenced in an article who have the same last name (e.g. Sydney Duncan and Andy Duncan), refer to them by their full names throughout the article to avoid confusion.