How do I start preparing for CISSP certification and how much time does it take for preparation?

It takes2-3 months, the trick is the spend minimum of1 hour every day, regularity is a must Use CISSP-All in One Guide from Shon Harris.
Look for cccure.org, an excellent site for CISSP resources and then leverage prmg.in for sample questionnaires.
First complete the CISSP guide, then take1-2 exams and then again read the guide, this will give an excellent perspective about what is expected from the exams