How can you easily see who done the booking from your calendar?

jacifieldUNC 
If you are using Personal Bookings, the only way I know to see the emails of those who booked with you is to go to your Outlook Calendar, there search for "Bookings". You can open each and see who your client that is under "Required".  Unfortunately, there's no way within Calendars to View a header Column that uses a Formula to see the STMP email addresses of the Required Attendees (unlike how you can do with the Email folders).

If you create a Share Bookings (instead of a Personal Bookings), then in its left pane you'll set up Services (AKA, an appointment type).  The Service you create can have the Custom Fields be required (such as email).  Then, after a customer or a few of them have scheduled Bookings with you, under this same Bookings' Services page, in the left column you can click Customers and you'll see all the emails that have scheduled bookings with you in the past.