I am not sure if my experience would benefit you all. I was facing the same challenge. But things change. I mean it. I have NOT taken the GMAT but I can tell you something.
Earlier when I used to practice/take tests - Math is OK. Atleast interesting to do. Prob/Stats is difficult. Difficult problems on other chapters - mind gets blocked.
Verbal - Sentence Correction-hit or loose. Reading Comprehension - absolute luck - cant understand anything out of the passage. Critical Reasoning - sometimes I feel, yes I know it. Sometimes, this is not my cup of tea.
Now - Math is definitely OK. Prob/Stats - need to brush up again and again not to keep forgetting.
Verbal - SC - is purely stratergy. Spot the type of error being tested.
RC - Yin/Yang words. CR - Try some difficult stuff (LSAT).
The reason for the change
1. Statergy/Tricks - whatever u call it. Others adapt to stratergies/tricks naturally or by reading books (kaplan/princeton). But for us, it comes thru repeatedly trying to understand the same thing.
2. Unlearn what we have learnt, accept what the guide has to say, try the method - see if it works for you. Some guides say - read the question stem first - test this approach whether it works for you.
3. Initially for a month, if you spend 40 mins for taking a test, spedn double the time (80 mins) for revising the answers - no joking. Revise, understand what went wrong.