Hey mate,
I found it difficult at the start too at was getting in the high 500s. In general I found that I skimmed over the basics and went to the hard questions early on. So I literally started again, I went through each of the
MGMAT quant books and read the SC bible. I did all the questions in both books and kept an
error log. I then did as many OG questions as I could. At this point I was able to identify a few weaknesses in quant and SC was still very difficult. I went back to the weak topics in
MGMAT and re-did them and re read SC bible, and did some more OG questions and saw a drastic improvement.
With CR and RC, it was much different, I had trouble absorbing most resources so I tried my own thing. First was visualisation, where I imagined each sentence as a movie or a cartoon. In RC I realised that when the question points you to a specific part of the passage, the answer lies how it relates to the overall context, that means you may need to re-read the few sentences both before and after where you are directed. In CR, after I visualised the scenario, thereby understanding it better, I realised that every piece of information is there for a reason. I would usually come down to two answers and then try and find a piece of information in the scenario which would somehow impact one of the two selections I was left with.
Finally, I focused on ensuring the ones that I should get right, I do get right and trying to minimise silly mistakes, ie ensuring I answer the question asked, not what I think was asked.
I saw my marks steadily improve. Fundamentally I believe that it is all about making sure your base is strong and then building on that one step at a time. Then OG OG OG OG and GMATPrep questions. I found that nothing else could supplement the style of the OG and GMATPrep type questions, even the old written ones (except GMAT Club questions)
Good Luck!