Hi Basavaraj:
The sequence of formalities to be followed is as follows.
1. The company should ask your eligibility U/S 224 (1B) of Companies Act, 1956 and willingness to accept appointment as auditor of that company by a letter.
2. You should confirm your eligibility and willingness by a return letter.
3. The company should inform you regarding your appointment as auditor in their AGM with a certified copy of the resolution.
4. You need to contact the retiring auditors seeking their no objection for acceptance of appointment (pls check if this needs to be done before receipt of appointment letter. In my understanding, it is after appointment from the company).
5. Receipt of no objection from retiring auditors.
6. You inform the company regarding acceptance of appointment and also intimate ROC/ MCA regarding this within 30 days of appointment (please check the latest provision in this regard as to who needs to do this now).
Hope the above is useful to you.