Fill out the form and double-check your entered details.
Obtain an account closure form, or one can download the ICICI bank account closure form online.
It will be best practice if you visit the nearest ICICI branch as you can obtain all the required information as well.
After transferring all of the funds from your bank account, keep a copy of your debit card, the first and last cheques in your chequebook, your account number, and make sure you have the customer ID with you.
One can even do this with your mobile phone net banking. You can do this online by going to the net banking website and transferring funds from your ICICI account to another bank account. The first step is to withdraw all funds from the ICICI bank.