Set a schedule, and stick to it. Designate two nights a week, where you are home and have free time, as your "class dates." Imagine if the class met twice a week at night (or during the day, depends on your schedule) and use that time to devote to the class.

If you choose Tuesday/Thursday, use Tuesdays as the day to get all of the reading done. Then use Thursday to get all of the assignments done. All other days are additional days to study for a test, get ahead with reading, etc.

I once took an entire semester of online classes-- 16 credits. I had to do homework almost every single day to stay caught up or be a little ahead. I stuck with a time and told myself, I was not leaving the computer until such-and-so assignment was done.