How can I change my surname? What are the legal formalities?

For change of name one has to get an affidavit prepared stating reasons for change of name and also the new name. Then the same needs to be published in two newspapers having wide circulation in your area, preferably one in English and other is the local language.

After due publication the same has to be published in gazette for notification with appropriate forms, fees and documents for publication.

After publication in gazette the new name comes into force and request for change of name can be made in all appropriate offices.