There are so many things I have to say about the experience of preparing for the CAT. However, I would stick to talking about things which really benefited me.
CAT has been changing over the years. And from what I see, it is essentially a test of logic. Last year they reduced the no. of questions to 90. Clearly the questions required more thought than ever before. So first of all you need to start thinking. There are many ways to solve a question. In CAT you have to arrive at the answer and this can be done without actually solving the question. There are many ways for this: one is to actually check for the answers option by option. You will realise this as you start taking tests. You will, and you should find such short-cuts. Even the Verbal Ability/Reading Comprehension questions are more logic-based than a mere test of English.
There are many ways to solve a question, especially in Quant. You should look for the method that is thought-based, rather than a mere application of formula. Many questions are so designed that a formula won't ever work. The most important tool that can help you get through is pattern recognition. Many questions in CAT can be solved by pattern recognition, without actually solving them, and some without even putting pen to paper. I am saying this from personal experience. CAT requires no great knowledge of English or Mathematics. All it requires is an uncluttered mind which can think fast and handle pressure. If you find a certain part really tough, concentrate on your strengths. You just need to clear the cut-offs in all the sections, and that isn't too high.
CAT is just an exam. All you need to do is prepare well and prepare consistently. I have seen many able candidates performing well below par because they didn't show enough enthusiasm. Be enthusiastic. Those 2.5 hours matter a lot. All you need to do is start thinking. Maybe solving a Sudoku could be a good exercise to start with.
Have YOU cracked CAT? Post your experiences. Mention your name, age, CAT percantile, B-School and where you currently work.