Just go to a Tata Dealer or SBI Branch or Croma Store or Westside Store. Take the booking form in Rs 300 to 500 and book it with the booking amount of Rs. 70,000. Wait for your number.
New Tata Nano with EasyShift is available at Rs. 2 lac (Ex-showroom, Delhi), and the final cost depends on the valuation of your car. So, first get the valuation of your car from authorized Tata dealer, so he can give you a final quote for the new car.