Introduce participants and build community
Provide opportunities for students to share interests and cluster
Allow students to incorporate interests in assessments
Community can be a powerful force in a course, aside from the amount of engagement can be rooted in community, there's the potential for community to explore and incorporate elements that wouldn't happen with the instructor alone. With the online class you may want to deliberately make community building a bigger element to the start of the course. You may want learners to contribute a low-stakes introduction like the "where you learn from" ice breaker. You might consider surveying students around their intent with the course and using that information to "stack the deck" for student discussion groups.
The where you learn from introduction
Setting up a Moodle Discussion Forum
Practical Tips for Engaging Students via Online Forums: Flower Darby
Clustering is a strategy that some learners use (either consciously or unknowingly) for large courses. Clustering happens when a student finds or forms a group with similar goals or interests, or generally gets along. You might want to help the clustering process by breaking a course with a lot of students up into smaller discussion groups and keeping those groups consistent for the course. Otherwise you may want to encourage students to share their goals, ambitions, questions, or course intent so they can connect with others who are on a similar path.
Success in an Massive Open Online Course
The goal of social presence in an online course is for students to be able to project themselves into an online course as their real selves. While there are ways to accomplish that aesthetically through things like images and avatars. However there are often ways to push this deeper, allowing students to channel the learning and assessments of the course into projects, activities, and discussions. You may let students choose the audience for an assignment, for example, if a student is taking a Foods and Nutrition course with the goal of becoming a doctor you might want to encourage them to create an infographic that would educate the general public about Canada's Food Guide.