Take a set of transfer papers (sales deed and transfer of ownership, printed on stamp papers). It also has delivery letter. The complete set is available with multiple vendors behind civic center, was 600rs or so last time I took. All taxes and dues must be cleared before transfer. After that, the file and signed transfer letter docs are submitted in civic center for the transfer with a fee. Vehicle is inspected by the authority at that time aswell. If you do it through some agent, vehicle inspection is somehow skipped. It takes around a week or so for the transfer process to be completed by them, after which the file can be taken back from the office.
Dont leave this process to be executed by buyer, as in most cases, dealers, will never get it transferred and will become a headache for you later on.