The most important aspect of facilitating online learning is to effectively communicate with your students. Since you may never even meet your students face-to-face, building a good relationship with them is crucial. Most online learning programs have various modes for communication between teacher and student, including discussion boards, live chat and email. Learn to use these tools, teach your students to use these tools, and remember to stay in regular contact. You should aim for some personal contact with every student at least once a week.
Let students know that the person teaching them and grading their assignments is a real person, not a robot. Post a picture of yourself and bio on the course home page and try to make the bio personal. Tell them how many kids you have, as well as your favorite hobbies and interests. Also, many online learning platforms allow professors to make videos with their webcams and upload them. Even if this is not a feature you will want to use regularly, consider posting a short intro video so students can see you and hear your voice.
Since you do not talk to students one-on-one, the only way you can measure progress and give them guidance is through responding to their work. Instead of the traditional midterm, final and term paper, give short assignments throughout the semester. Grade and return these promptly and use your comments to tell students what they are doing well and where they need to improve.
The possibility of cheating and plagiarism is always a problem for teachers, but it increases exponentially online. Though online learning platforms try to prevent it, it is far too easy for online students to cheat on a multiple-choice test drawn from a question bank. Use short-answer or essay tests or other modes of assessment, such as essays or creative projects.