We Often Forget what we learn unless we have practical experience of our learning Or whenever we feel, particular topic is complex; that mindset makes us forget. 

So, My way of taking notes from online courses is to WRITE the IMPORTANT Stuff; I know shorthand, so its easy for me to take stuff onto paper. Let's say whenever am going through a course, if at all am spending 20 mins on particular class; then the subsequent 5 - 10 mins, i will spend on analysing it and taking the same information to EVERNOTE. Taking everything to EVERNOTE is not possible, so mostly the topics i am hearing first time, i will mark into evernote, with pictures if possible.