Regulations : It is illegal to bring Indian currency into the country. There is no limit to the amount of foreign currency you can bring in. Anything over USD 10000 should be declared on arrival. Please insist on the encashment certificates. Without then you cannot reconvert your unspent money while departing.
Credit Cards (Amex, Diners, Master, Visa) are widely accepted throughout the country. There might be a problem of acceptance in certain rural areas.
Travellers cheques : Popular brans of travelers cheques like AMEX, Thomas Cook, Citi Bank, etc widely accepted. However some organization like Indian Airlines accept TCs only from biggest companies.
