--Schedule office hours that accommodate a variety of typical schedules. If possible, set both morning and afternoon sessions that cut across normal class times. This will increase your availability for your students and it will decrease the amount of extra appointments you will have to make with your students.
--Include your office hours in the syllabus.
--Be present during office hours. Of course, make sure that you are there physically, but also be mentally and emotionally prepared to help your students with their needs. Put your work and personal affairs aside for that time.
--Check with your department regarding their specific policies related to office hours. Each department governs the amount of time and other office hour requirements based on their particular needs.
--If you will not be available during an office hour, try to announce your cancellation to the class or post a note on your office door with other contact/appointment information.
--Don't forget to set time aside for yourself. If a student shows up to your office and expects help during a time that is not designated as an office hour, explain that you would be more than happy to help them and set an appointment at another time convenient for you both.