My first flight with BA was 1978 to ORD, our starting point was Victoria where we checked in - I would love to do that now !
I seem to recall we got sent a magazine and joined a club called 'friends and family overseas' - we got paged at the airport (T3 airside) and met a representative from the club, BA employee I think, who gave us 'tips' about the US.
It was a very naive time for leisure travellers going long haul, so much has changed since that time - it would be assumed you know what you are doing nowadays.