Upgrade from 2.3 to 3.0

Hello...sorry if I posted this before....just learning my way around your forum system.

I have questions about this wiki entry - http://pve.proxmox.com/wiki/Upgrade_from_2.3_to_3.0

It states the following - "Before you start, make sure you have a valid backup of all your settings, VM´s and CT´s."

What is the best way to achieve valid backup of all settings?

Thanks.