The best way of accessing cash in India is to withdraw it from any local ATM using your bank debit card, as long as it has Visa or Mastercard logo (a few other logo are also supported by ATMs). It will attract some additional charges for international access and currency conversion charges, but it is hassle-free. Please review Facilities page for more details.
Most businesses will accept debit and credit cards (American Express cards have much less acceptance than Visa and Mastercard) so you do not need to carry cash in most cases.
Carrying USD 50 worth of cash (INR 4000) at all times should be good enough for most eventualities.