Chennai (Madras) is a major city in the South.
Kochi (Cochin) is the largest city in Kerala, one of the more modern, most educated states in India. Tourist will like it that most women still wear sarees and punjabis, not jeans. Kathakali dance is interesting, but very very very slow.
The backwaters are wetlands in Kerala, close to Aleppey. You can rent a comfortable boat for one or more days/nights and let the landscape pass by. The crew will prepare your diner, you take care of your pictures and the mosquitos.
Mysore, also known as Mysuru, is a pleasant city in Southern India with markets and the Sultan´s palace. Mysore is a great stop when visiting Ooty or Goa as well.
Mumbai, formerly known as Bombay, is the economic centre of India and a world-city. There are lots of places to visit including the Gateway To India and Bollywood. If you have some money to spend, stay at the Taj Mahal hotel... a place with tradition...
Capital of the state Goa with many Portuguese and Christian influences.
Jaipur is capital of Rajasthan. It takes it's nickname, the Pink City, from pink colored buildings incl. Wind Palace. Nearby is the beautiful Amer/Amber fort/palace, that you could enter on the back of an elephant... Delhi, Agra and Jaipur together form the "Golden Triangle".