To start your preparation for CAT first of all you need to understand the pattern of CAT it consists of three sections quantitative aptitude, verbal and reading comprehension, logical reasoning and data interpretation.once you get well aware of the syllabus then you can divide a timetable and based on your Earlier knowledge you can give time to the different sections so if you are someone from mathematics background then you will find quantitative aptitude to be easier and if you are someone from language background then verbal and reading comprehension will be easier for you there for it was a point depends upon your background that which part will be easier for you.