Problem with verbal is that we in India follow British English and the GMAT tests American english. Is GMAT fair for non-native speakers. No! But does getting a good score in verbal means that a person has mastery of English. Definitely! There is no way around it.
English has always been my serious drawback. I started from basics as I couldn't remember what was preposition, adjective, adverb, etc. (a little bit of exaggeration) . But you do get the point.
1. I started with "Painless Grammar" by Rebecca M. Elliot. So that I can understand what the books such as Manhattan SC were talking about. Now you may be getting at what level I was!
2. Did Manhattan Sentence Correction.
3. Kaplan Verbal - though it has some good tips for AWA and reading comprehension, it doesn't have a lot of questions for practice. My biggest take was to understand how the RC works. It's very crisp, but some very good tips in there.
4. OG 12 and the verbal supplement. I think the best strategy is to not find the right answer, but to figure out what's wrong with the wrong answers.
5. A lot of online websites such as gmatclub and beatthegmat have good discussion forums where a lot of good questions are posted. You can have a look at them.
I think that after a certain level in the real GMAT exam, the GMAT becomes like someone firing towards you with a machine gun. You need to duck and take cover at certain times. You can't be a perfectionist. You need to know which battles to pick and which battles to lose. The end result should be to win the war. Always keep an eye on your biggest adversary, i.e. the clock.
Let me know if you want to know more. Try to focus on your weaknesses. Mine was English, but I think it's not that bad anymore. Be confident and don't let your nerves get over you.
At the hardest levels in the GMAT, the GMAT starts playing tricks on you. The questions look tougher, but they really test the same basics. I got a graph in Quant and the entire question was 4 pages long, but the real question hidden within it was very small.
For quant, the Manhattan Advanced Maths book was great. Previously, I used to focus on questions and then to arrive at the result. You need to think both ways.
Thanks