Satish,
you need reference letters from all of your employers (exp that you want to show). It should clearly state the designation, dates of employment, duties (try to match with the ones on ACS site), manager or HR name and designation. This should be on company letter head with business address n telephone numbers.
My agent asked me to get any possible documents that i can lay my hands on from the company (offer letter, appointment letter, increment letter, promotion letter, releiving letter, pay slips, form 16 and tax documents).
I am not sure which of these were sent to ACS but i think they will be needed when you apply for DIAC which will check for your experience.
Why do you need to use an agent in India? Your agent can be anywhere in the world as the work can be carried out over the phone and via email.
Thanks a lot for your quick and prompt response. I have got his migration agent number and verified in "mara", then let me proceed with Australia guy.
Btw, can you help me in getting the list of documents that need to be submitted to ACS for employment assessment.