Backup Database Question

So I'm looking to start regularly backing up my production database at
work. I'm tired of doing it manually every day before I go home. I use
the built in 'pg_dump' or 'pg_dumpall' utilities however I don't know
which is more beneficial for a nightly backup. Perhaps I should be
using the 'pg_dumpall' as a weekly / full backup only and not perform
this nightly but honestly I have no idea so I'm asking the experts
here. When should I use 'pg_dump' & 'pg_dumpall'? Is there a downside
to just backing up the entire database cluster nightly besides I/O
load and sacrificing system performance?

My last question is does anyone know how I can easily automate my
backups for PostgreSQL in Linux using Cron or some well written script
someone has on the web? I'm looking for anything that can simplify
and automate my backups for me so I don't have to do them manually by
hand before I leave the office.

Thanks for any help in this area!