Where can get GMAT preparation study material online.
Also please share your experience with GMAT and high scoring!!

Hi,
I suggest you this forum:
http://gmatclub.com/
it's pretty good.

A good place to start is with an online practice test (Princeton Review, Kaplan, Manhattan all offer them, for free) to target your strengths and weaknesses. Depending on how well you do, you can either address your weaknesses in self-guided study, or if you've done really poorly, you can pay for test preparation help.

It's a bit difficult to gauge your performance on the writing and integrated reasoning sections - so I'd recommend having a native English speaker read over your essays for feedback.