You can find a single subscriber in a matter of minutes by selecting Subscribers > Search in your left-hand menu:
Then typing the reader's email address, and click search.
The following screen will display a table of results. Select the email address of the subscriber:
On the next screen you will see all the information available for a particular subscriber including their subscription, tagging and custom field information as well:
As always, if you have any questions, please don't hesitate to let us know. You can find all of our great support resources and how to get in touch with us via email, chat or phone on our Support Page.