A very difficult question to answer since India is so vast and diverse. It is each to himself or herself depending upon what you wish to see during your travel in India. For lovers of archeology historical places in New Delhi and Agra are must visit, as for example the "Taj Mahal" Delhi Fort, Kutub Minar and Fatehpur Sikri.
For the lovers of Indian desert life it is a trip to vast stretches of Rajasthan to live in Maharaja style in the palaces in Udaipur, Jaipur and Jaisalmer to name few. Rajasthan has a rich colorful culture to offer to the visitors. Bharatpur offers excellent bird watching to birders and is one of finest birding destinations in India.
Central India offers best tiger safaris to wildlife enthusiasts. Kanha, Bandhavgarh and Pench are popular tiger reserves in India. Pachmarhi is a pristine, unspoiled little paradise for holidaying at high places. It is a popular hill station in Madhya Pradesh.
These posts are going to highlight best places to see in India so keep subscribe if you wish to know about the places to visit in India.