A mix. Learn chapter by chapter, and try a couple of OG problems to test out the concepts, but then return to the next chapter. Don't use up all the OG problems in this way.
As you advance through other chapters, you may also toss in some OG questions from earlier chapters - eg, once you're halfway through the book, try a mix of questions from all previous chapters. The further you get, the more your practice should consist of a mix rather than just one topic area.
Also, make sure that you're doing smaller sets of questions, maybe 5 at first, then maybe 10 for mixed question sets later on. Don't do 20+ problems in a set - all you're doing is wasting a bunch of questions. Do a small set, learn from it, then do another small set, etc. Periodically, you'll do a larger set or a practice test, but only periodically.
You might find this useful, particularly the "how to learn" section in the second half of the article:
http://www.manhattangmat.com/blog/index ... an-part-1/Also, you said you already asked once but didn't get a response. Can you direct me to that post? I don't see any missed posts anywhere in this folder - just the ones from the last couple of days that I haven't gotten to yet.
If you posted in one of the content-area folders, it typically takes longer to get a response in those folders. If you are just asking a strategy question (not posting a specific problem), please feel free to post in this folder!