There is a booking form that can be procured from any authorized Tata Dealer, any State Bank Of India Branch, Westside Retail shops, Croma Electronics retail stores at Rs 300. You have to submit that form with booking amount to book Tata Nano.
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.