N00b To ER Modelling, Please Help!

Okay, can anyone help me with the following:-

I have to create a database on theatre booking system. So far, ive identified the following entities:

Customer(Customer ID, Title, Initials, Surname) Customer ID is PK
Bookings(-------)
Play(Playname, Playwright, Number Of Characters, Length(min)) Playname is PK
Actors(-------)

i do not know what to create as attributes for the bookings table, especially seeing as the attributes have to relate to customer and play. for the actors table i was thinking of putting in the following attributes:-

Actor ID, Name, Age, Playname, Role (Actor ID is PK)

but i was unsure if they worked, although i think they would, because playname from the play table would be a foreign key in the actors table. this is where i come into conflict with the bookings table, ie what could add to teh custoemr table as a primary key that would make a suitable foreign key in the bookings table, and what could be a suitable primary key in teh bookings table, and also a suitable foreign key in the play table? please help, its an urgent issue. thanks very much for your time.

Fergal