(This is one article in a series offering tips for teaching online. The suggestions and ideas shared are based solely on my personal experience teaching online for many years, and not on any "hard" research.)
Teaching online is different from teaching in a face-to-face classroom in a variety of ways. One often-overlooked difference is the access needs of online students to the instructor.
When I began teaching online, I tried holding regular "office hours" via online text and video chats, sitting hours by the computer waiting for my students to "arrive" in the chat or video call who never came, only to receive emails or chat requests from students an hour or two later or the next morning, when they were able to be online, asking for help. It struck me that adopting the same accessibility policy I had for my face-to-face classroom for my online classes - i.e., having set office hours on set days of the week - will not work for my online students. With access to the course varying across students from day to day and week to week, there was no way holding regular office hours at set times would serve my students' needs.
To best meet these needs, then, I adopted a policy of being accessible to my students 24/7. I try to remain accessible to my students when they need me, and not when it is merely convenient to me. Evenings? Absolutely! Weekends? All the time (that's when my online students seem to work in their courses most commonly). Middle of the night?!? If I am awake, and see/hear the message, yes, though such requests are rare (contrary to popular belief, students do sleep!).
To foster my accessibility, I inform students the best way to contact me is through a direct message on Google+ (a social media communication platform. Students in my online courses are required to have a free Google+ account). When they do connect with me through Google+, I receive a audible notification on my mobile device that informs me immediately a student needs assistance. While I can and do receive student requests for help through email, I receive more emails from a variety of sources on a variety of subjects than direct messages through Google+, so an email notification may be more likely to be missed if it arrives with other messages, and consequently its response may be delayed (for my personal well being, I try to tackle my email only once or twice a day!). That is, when I hear the notification sound for a direct Google+ message, I know a student student needs my assistance right now.
When able, I respond to each student's request for assistance immediately. Doing so allows me to communicate with students while they are still online, working in the course. Often, my reply evolves into a back-and-forth "conversation" with the student during which issues are resolved, and others frequently come to light. Email is much less immediate, and if your email reply is delayed even by one day, the student may not see your email for several more days, depending on when s/he is able to be online. Consequently, the immediacy of your assistance is lost, and as a result, may prove far less helpful (and more frustrating) for your student.
Has making myself accessible 24/7 for my online students a significant burden? Not at all. Usually, after the first week or so, the frequency of student questions drops off dramatically. In fact, making myself more accessible has actually saved me time, in that I no longer sit for hours by the computer waiting for students to "show up" at scheduled office hours. And, if you have crafted carefully your course syllabus, course schedule, and assignment instructions, everything in your online course should work smoothly, for the most part, without the need for frequent instructor direction.
I feel it is important, as a teacher, to do all that I can to help my students succeed in my course - online or otherwise. Making myself readily accessible to my students when they most need me is a small step I can take to help secure student success.