How do I map fields while importing tasks?

How do I map fields while importing tasks?

Hi,

I am trying to import tasks from from another CRM to Zoho.  I am not sure of the values expected in the field mappings. 

I started by exporting a set of tasks from Zoho CRM itself and import back the same.  The tasks are getting imported, but the following fields are missed out.

Due Date - My file has this in dd-mm-yyyy format and I chose the same in advanced options.
Contact Name - Should I give the contact name or contact id here.  I tried giving both; neither works.
Related To  - Should I give the potential name or potential id here.  Both doesn't work.

Any sample mapping file would be helpful.

Regards,
Janaki