steps to ensure referential integrity

I have inherited a database that was originally created in postgres
version 6.? There were no steps taken at that time to implement
constraints to ensure referential integrity. There are no FK
constraints, PK constraints, etc..
Most of what currently exists is done in the existing code. I would like
to change this and am interested in getting suggestions. I expect that
PK constraints on each table as well as all FK constraints should be in
place. Anything else that I should consider?
I have indexes currently set up on a variety of fields, including PK
fields. Do the constraints automatically generate indexes on these
fields such that I should remove the ones created at the end of my script?
Thanks in advance for the suggestions!
Jodi
--

_______________________________
Jodi L Kanter
BioInformatics Database Administrator
University of Virginia
(434) 924-2846
jkanter(at)virginia(dot)edu <mailto:jkanter(at)virginia(dot)edu>