LOGON FREQUENTLY. Log on at least three times a week, e.g., MWF or TTHS. I highly recommend logging on daily. If you're highly motivated, I'd recommend twice a day, once in the morning and once in the evening. On weekends and holidays, log in at least once. Create a workable logon schedule, a comfortable routine that works for you, and you'll find the workload manageable. If you let days go by before logging on, email and announcements will accumulate and you'll find it difficult to catch up. Also, you'll find yourself outside the communication loop and out of synch with classmates, unable to understand what's going on. Again, don't expect the instructor or your classmates to remind you about deadlines or guidelines. Being informed is your responsibility.
PACE YOURSELF. The potential for being overwhelmed is ever present, especially at the beginning of the semester (or summer session). Because most of the course information is available all at once, some students are tempted to (or believe that they need to) master it all at once. Just as you can't learn everything a course offers in one class period, you shouldn't expect to master the contents of an entire online class in one or two sessions. Keep in mind that you have weeks and months to do so. Thus, the key to success in an online class is awareness and pacing. Via the assignment calendar, become aware of what you need to learn and when you need to have that information or knowledge. Next, pace yourself. Just as you wouldn't try to complete a marathon by sprinting at your top speed, you shouldn't try to learn everything in one sitting. Divide the learning task into smaller manageable chunks that you can master in 30-60 minute intervals, and spread them out over two or more sessions -- or days or weeks if the material is especially complex.