1) Well usually for SC, I try finding the mistakes when I read the actual given statement, on the basis of the mistakes I find and the available splits, I eliminate options and then I evaluate the remaining 2 or 3 options in a more detailed manner.
For RC, I first read the passage, make small notes for each paragraph, try to determine the the purpose of each paragraph and that of the overall passage. I came across this technique of active reading, that is trying to understand the purpose of every transition word etc. I had a hard time on one of these passages in my exam, it was a passage based on zoology. While attempting questions, I first try searching for the answer before seeing the options in inference based, primary purpose, specific detail questions.
For CR, first I determine the question type, then I read the question stem, try to think of an answer before looking at the options (though i must admit, I find this hard to do on the more difficult questions), while choosing my answer I eliminate all those answer choices which I think are wrong or irrelevant and then choose the correct answer.
2)This happens very often, more often than I would want it to often. Sometimes I find it hard to choose between the 2 even after spending close to 1 minute evaluating the 2 choices and then ultimately marking the wrong answer choice.
3)Yes timing is a problem, I am quick with my SC questions but not so much with CR and RC questions. I also struggled to finish my section on time in my last attempt and had to rush a towards the end as I understand that leaving a question unanswered implies a bigger penalty.
Thanks again Rich!