I am an exclusive online instructor. I welcome each of my students into the program via telephone once I receive notification of a new student, and follow up with them weekly (either through telephone or email) to ensure they don't feel alone in the program.
I do notice that a few of my students won't contact me if they have questions. I explain to them from the get-go that since we are entirely online, I am unable to look across a classroom for visual cues that a student may be struggling with a concept (or just needs the concept explained… >>>