Go to a currency-exchange information site, such as x-rates.com, that gives cross-rates for the rupee against all other currencies. The site will give a table of today's exchange rates from euros to rupees, and rupees to euros. Charts at Yahoo Finance show historical rates and current trends. Simply entering "rupee to euro exchange rate" in the Google search engine will bring up an instant quote, given in boldface at the top of the search results page.
Of course, the Internet can't physically exchange currencies for you. If you hold euros, you will have to go to a bank or currency exchange shop and request today's exchange rate. You will be quoted the number of rupees they will pay for a single euro. The rate may be listed on an electronic rate-quote board. The bank or business may offer different rates for cash and traveler's checks. Some of these operations can also use a cash withdrawal taken from your credit card, although caution should be exercised.
You will not be able to exchange for rupees before you arrive in India, as rupees are not available outside the country. There is always an exchange desk open at an international airport. Ignore anyone who offers you a better exchange rate outside of banks and licensed currency exchange shops. Unofficial (black market) currency exchange is illegal in India. Since the currency is stable, freely convertible and allowed to float on the international markets, there is little incentive for black-market exchange.
It is a good idea to exchange only that amount of money you will need for a few days, and bring a pocket calculator to the transaction. During the exchange, you will be asked for your passport as identification. The bank or bureau will charge a commission and keep a record of the transaction, and you will be given a receipt. Keep this document in a safe place; you may be asked to produce it upon leaving the country. Ask for smaller denominations and don't accept torn notes--many places of business will not accept them. Verify that you have the correct amount before you leave the premises.
At the end of your trip, you can sell your rupees for euros again at banks and bureaus. Don't wait until your return home to exchange. Hold your receipts to prove you have only been exchanging money through legitimate channels. It is not legal to take Indian currency out of the country, although in practice tourists and business travelers are not searched for currency before leaving India.
