INSERT question

Hi everyone,
I've a little question about using insert statements. I've got a
parent table with a "serial" (automatically incrementing integer)
primary key. I have a child table with a foreign key which references
that primary key. My question is:

To insert values into the child table corresponding to an entry in the
parent table, how do I get a reference to the serial primary key (so
as I can reference it for the foreign key entry)

Hope you understand what I mean. This should be a regular occurance
and seeing as I'm not an sql guru, I just don't have a clue!

Any help would be SOOO appreciated.
Brian