Dear Sathya,
Headhunting is the process to approach people working into same industry which suits the profile you are working upon even though you don't have his direct contact details. You have to figure out who are the most suitable candidates for the profile and then you have to contact them may be through Social Networking Sites or Company Phone Number which he working with or may be through some other sources. People often get confuse with the terms Referencing and Headhunting being the same, but referencing is just a part of headhunting. If you have any more confusion please feel free to ask.
Regards,
Kumar Ashutosh,
8527402747