This is what I do for my data:
a) 1st level of back up is to a separate backup internal hard disk that uses Windows file history to backup every hour.
b) 2nd level to an external RAID enclosure via a continuous data backup (CDB) software AND a data synching software. One such enclosure is marked as an offsite backup.
c) 3rd level to another PC on my home network.
d) 4th level to a NAS enclosure on the network, set up for manual data synch.
I don't use optical media as they are slow. My Blu ray & DVD writers are mostly used for read only functions and once in a while to create audio CDs

I may be interested in cloud. Interestingly MS has been giving out unlimited space on their OneDrive cloud storage to some Office 2013/365 users. Just got a notification today.
My choice of cloud for non critical data is Dropbox though I have been a wary of putting up personal data on the internet.