If you are looking for free CAT exam papers of previous years, which you can download and use, then it is very easy. If you already under some coaching institute they will provide it to you at no extra cost then you can go to TestFunda.com. Sign up and once you are logged in you will find these papers under free resources section. If you are too lazy, just check that out over here.
Not only can you download previous year CAT paper, you can actually attempt these online on the same website for free. !! But before you go on and start with this, find time to read about how to prepare for CAT 2012 or find out about what kind of CAT questions are asked under CAT exam questions if you are a newbie.
You may also consider launching the exam of XAT or CAT online if you consider yourself prepared just to check out how it feels like by going over here. Please be careful while managing your time and also note that the pattern of old paper is not the same as the new pattern and the difficulty level of these paper is also not the same.
You may also be interested in finding about national cut off for old paper in order to related your own performance with the same.