Like with any site, backups are critical. Come join us in May to learn some tips and tricks on how to backup your EE site on a regular basis.
Update: Eric Lamb of Mithra62 will be presenting via Skype. After all, with an add-on like Backup Pro, Eric knows a thing or two about backing up EE sites! :) You can buy Backup Pro and Eric's other add-ons on Devot:ee.