1st attempt 670 (q50, v30) - disappointed

This is my first message in the forum, although I have spent almost 50% of my preparation time with the questions posted here. So, first, I would also like to thank you all for sharing so many questions from different sources and posting your solutions and approaches. It has been really helpful.

I took the gmat last week and still wondering what happened. My preparation exam results (I also did AWA and IR in all the exams as well as 8 minute breaks) from GmatPrep were 690 (q48, v36), 680 (q47, v36), 690 (q49, v35) and 720 (q50, v38). I did not retake any of the exams (I bought the two extra exams), so the results should be pretty accurate of my performance.

What freaks me out the most is the decline in verbal. As a non native speaker, I have faced difficulties, overall, with SC. In all my exams I got wrong more or less 10 questions in verbal, and between 80 and 90% of them were SC. I realized I had always been focusing on understanding English, and SC is a total different thing. And that is why I studied SC MGMAT (went through it two times, took notes first time and improved them the second time, and did all the exercises). I frankly believe it helped improve, I had more fundamentals to use to discard choices, but when it come down to two options without [obvious] grammatical errors, I was unable to identify most of the "wordiness" or "awkwardness".

What do you guys think I could do to improve my verbal? I have been reading for an hour every day of my preparation (1 month and a half) and read every day one or two articles in the economist. Maybe try some other guide, like Aristotle? I am having a break now and will retake in some months, with another month or so for preparation.

I would also like to add some things I have learnt while preparing for the gmat that I hope someone had told me when I first started. I hope it can help someone:

- Preparation is about improving. If you do not know your weaknesses the return of your time will be much lower than if you know them. Spend the first days trying to assess that.
- Once you know which are you weaknesses, work on them. Some people say that it is better to focus on your strengths but, in general I disagree because of the GMAT algorithm - if you are very good at PS, but terrible at DS, you can be able to do the most difficult probability problems, but they will never appear in you exam, since DS errors will make the algorithm give you easier questions. In my case, my quant score improved only when I realized I always failed in the exams the probability problems. As soon as I focused on that and mastered probability in two or three days, my quant score went up to 50
- Do not prepare as your friend did. Or maybe do so, but because you are convinced that that way you will earn the best return on your time. Not even if s/he has scored 750. Everyone has its own weaknesses and you must be able to assess them to pick the best resources to achieve your score. Maybe your friend was crap at CR and needed Pwerscore CR Bible, but for you it would be better to invest that time in learning more about number theory.
- Have in mind a target score that is reasonable for the preparation time you have and you objectives. Although I believe everyone can score above 700, some people may take it two weeks and some others will need 2 years. But try that your objective is realistic so that your mock score do not bring you down
- Do a test early in your preparation. Again, for getting somewhere, you first need to know where you are.