Hi Karan0912.
The main thing to do during the last week is keep going with your prep.
Keep working on weaker areas, and also seek to reduce the number of careless errors that you make. It's important to do whatever you can to make your performance consistent so that you achieve your goal score on test day.
On the last two days before your test, you should taper down your prep so that you're in your best form on test day, but keep preparing some even on the day before your test to stay in game mode.
Be sure to review formulas and strategies and practice any you feel shaky in using.
On test day, warm up before your test to get into GMAT mode before you see the first question, and be intense all the way through the test to maximize your performance.