It's been
discussed here before.
Currently I both do an export and an rman hotbackup every night,
although some of the larger (data warehouse type stuff) tablespaces I
may only export once per week, if the server they're on is old and
slow. The export and hotbackup files then go to tape.
I've tweaked those scripts I posted them a year, but they do basically
the same thing. The script are also a bit baroque in places (the
various options and redirection of output and such), but that seemed
useful when I was testing them.