During the 1st and 2nd phase of imp. u will gather all the necessary info. regarding the process from the client end,then u r responsible to create the AS-IS doc. and TO-BE doc.
AS-IS doc is the detail documentation of the existing system/process that the client's r using and TO-BE doc. is the implemented system/process that u wanna set up as per as the client specification.Thorough interaction b/w the client and the implementer is very much necessary during this kind of documentation...
Regards
Partha