@tarun1110 For starters, start reading a book. It can be anything. I will suggest the following:1. Life of Pi by Yann Martel
2. Shantaram by Gregory David Roberts
3. The Day of the Jackal by Frederick Forsyth
4. The Blind Man of Seville by Robert Wilson
And so on....
Do some homework on the author, his other works, try to zero down on a few of his books and try and get some idea about the story. This will help you to talk for 2-3 mins about any book or author you have read recently.
Keep yourself abreast of all current affairs - starting from Arvind Kejriwal to Yo Yo Honey Singh. Have an in-depth understanding and opinion about few vital topics.
Try to learn about the institute and famous Alumni (Aruna Jayanthi, for example, who is currently CEO, Capgemini India) and a few professors who are of repute. In short - DO YOUR HOMEWORK on NMIMS. Nothing impresses a panel more than prior knowledge about an institution/organization.
Hone your communication skills as much as possible. If required record yourself using the webcam of your laptops when you recite the answers prepared by you. Only when you see yourself on screen you'll know your shortcomings better. Trust me, your communication skills can cover for a lot of shortcomings.
Learn a few basic economic and financial terms and if possible any example to relate to - for example, the Demand-Supply curve, Game-Theory, Nash Equilibrium,
Prisoner's Dilemma, Repo-rates, CRR, etc. (I was given a case-study on
prisoner's dilemma, last year. I knew it along with one more guy in my GD group. Eventually we two made it 
)
Prepare your SOP well. Make it meaningful and don't lie.
More when we start the GD/PI thread.
Good luck till then :)
Perhaps the top of the mountain is cold, but the view more than compensates for it!