trigger that needs a PK

Hi,
I'm sure this question has been ask before but I could not find anything on 
google.  I most likely did not enter the right text into the google search.

I have a parent table that requires that an insert into a child table happen.  
The problem is I can not determine what the parent pk is for the insert into 
the child because it hasn't happen yet - if I set the trigger to before 
insert.  So I guess I need something that works with after insert into the 
parent so the pkid can be created.

The parent has:
pkid serial
lot varchar 30

the child:
pkid serial
fk_parent int
other fields....

The question is how can I get the pk and insert it into the child.  Of course 
I'm new so if I missed something just provide the link or tutorial.  

Thanks in advance!


-- 
John Fabiani