Backing Up a Postgres database...

Hello, I'm not sure who I should be posing this question to but I'm a
System Administrator who has inherited several Debian Linux servers one
of which apparently hosts a rather large Postgres database.  One of my
responsibilites is to back that database up each night and be able to
recover it "on the fly" in the event of a problem.  I have no idea how
to even check which version of Postgres is loaded on this server, let
alone, be able to back it up.

Is there anyone who can give me just some basic commands on how to shut
it down each night, back it up, verify that the back up is good and what
to do in the event that I ever have to restore it?  I know it seems like
a lot but I'm swamped with a million things to do and would rather not
have to read a couple hundred pages of material if I can avoid it.

Thanks in advance,

Jon