Hi yuvaraja,
Since there are plenty of options for you to use during your studies (books, Courses, Tutors, websites, etc.), it might seem like a daunting task to decide which resources to use. It's safe to say that each of the resources that you might investigate has helped someone to prepare for the GMAT, so the real question is if those same resources will help YOU to succeed.
It's a good idea to take an initial practice CAT to get a sense for what your natural ability is. You probably won't be happy with that first score, but that's okay. Most people don't do particularly well at the start. Once that score is established, you'll have a sense of what you'll need to work on. From there, you should investigate the various options. Most GMAT Companies offer free resources that you can use to get started and decide if you'd like to purchase additional resources. You can decide which resources best fit your personality, timeframe and budget. The Forums here also provide a great opportunity to pose questions and get advice from a variety of experts.
You'll probably find this to be a challenging task, but don't get discourage. The GMAT is a predictable exam, so it can be prepared for and beaten.
GMAT assassins aren't born, they're made,
Rich
