File System Restore

I'm running the latest version of PostgreSQL.  I backed up one of my
databases following the instructions in the postgresql documentation.
This means that I did shut down postmaster and I tarred the data
directory just like it says to.  Now, I'd like to restore the file
system.  I started by just copying the data directory back, but that
hasn't worked for me.  Can somebody please give me some detailed
directions on restoring the file system correctly.  I think the only
thing that is different about this new install of postgresql is that it
is owned by a different user than before.  Thanks.

-Carter