Get a Garmin GPS unit. See here: *www.garmin.com/garmin/cms/us/ontheroad/nuviseries
These work quite well in India. There are maps available for all major cities. Interestingly Autocar India made a special test last month in Mumbai which had three cars with drivers who weren't from Mumbai and hence didn't know the streets here. They had to navigate to a set route. One car had the help of a GPS unit, one had regular map of Mumbai and one asked directions from people. The car which won was the one using the GPS unit. It came in the shortest time and used the shortest route to the destination. You can read about it in the December '07 issue of Autocar India.