If you don’t know your Google Account password, follow these steps to set a new one.
Go to the trouble signing in page.
Select “I don’t know my password.”
Enter your email address and follow the instructions on the screen.
As fast as my experience go it is impossible to find the recovery information associated with a Google Account without the consent of account’s owner.
What you can do is use some social engineering skills. Gmail security is pretty solid so don’t expect to break it so easily. If the account has a recovery email id associated with it you can choose the forget password option and then choose to verify via recovery recovery email. The screen shot looks like this.
or some of this sites (to retrieve user ID):
Note : This is not my account. I just used a random account.
You will get to know the first and last digit of email address along with the service provider. So you can social engineer the account owner and determine his recovery email account.
This may not work for all accounts. Accounts that have 2-step verification enabled needs to be verified that way for password recovery. You can not simply get recovery email address for those accounts – Not even first and last characters.