The only way to search for a subscriber is by using an email from the dashboard and that's not very optimal.
I needed to find a subscriber with his name only and I had to go manually through each one of my lists to find him.
The same would apply to additional fields — I want to look for subscribers born in 1986. Ideally this would be done with a datetime custom field and with a filter for the date.
But to make things simpler: I want to look for male subscribers — Custom field: Gender, Value: Male.