How to select dates and times of office hours for the benefit of students and instructors? Office hours can be selected at any time, but how they can be selected to benefit all? The students to ask the instructors and the instructors to have some time to conduct research? Before a class or after a class? In the same days as the class, days with no classes, or all days?
If I had a two day a week class, I would have it before class on Tuesday, and after class on Thursday.  And also by arrangement, if someone couldn't come because of their class or work schedule.

At my school, the rule was two hours for each class.  There's no recommended amount of time where you are?