best way to setup postgres as backend for webapp?

I want to use postgres as the back-end for a web application.  Postgres
is installed and running on a Red Hat 9 server.  I'll use python to
handle the connection.  What is the best (easiest + safest) way to set
up postgres as the backend?

Should I create a user called 'mywebapp' and then use that user in all
my python scripts?  And should I make a database that is owned by user
'mywebapp'?

Also, although I use the -P flag with createuser, I still am not getting
prompted for a password.  Do I need to change my pg_hba.conf file to
something like:

local   all all ident   md5

Thanks for the help.