I really think this is a personal decision that each student has to figure out for him or herself. As for me, I have changed my methodology several times in the year that I have been studying. What ended up seeming most efficient for me is to study an audio lesson, and incorporate the section of the beginner's book and/or language and culture lesson that deals with the same subject. Of course, not all of them have parallel subjects, but when they do, they seem to reinforce each other in my mind. Also, now that I am in the Premium Plus course the audio and language/culture lessons seem more aligned, which I like a lot.
One other thing that I have found helpful is to use the Scriptorium Technique found in the My Toolbox section. What I did was to go back to lesson 1 in the Premium course and begin writing out the sentences and phrases in the testing sections as suggested in the technique. It has reinforced some grammar and vocab I may have forgotten, and I am amazed at how much more sense some of the grammer and verb conjugations that confused me first time through is making now. I may actually be learning this language!