If there's one thing you're going to install, Make it Akeeba Backup!
That's right. Akeeba Backup is FREE (paid version available with more features) and prevents data loss. Akeeba backup simply backs up your Joomla! site and the database by default so your can always restore or migrate the site! It's that easy. Even web hosting company, CloudAccess.net features at the core, a restore solution where you just upload your backup and restore it to either the same domain name or choose a new one.
There is no second option to Akeeba Backup
We've used Akeeba Backup on every site we've created. We do use the paid version as it allows you to schedule backups as well as encrypt them, server to server transfers, incremental and database only backups as well as a whole host of other features [Pro (paid) vs Core (free) features], and it's only €40!
One Click Backups
Akeeba will backup your site in one click. It's that easy. Just install, let it do it's initial configuration checks, and click to back up. No fuss, no mess. Nic Dionysopoulos [https://twitter.com/joovlaki] really developed one of the best Joomla! plugins ever, and by the way, he contributed Framework on Framework (FOF) that was integrated into Joomla! Core.
Akeeba can backup your site automatically! Never have to worry about losing data again! Your backup can be downloaded or transferred elsewhere in case of server crashes.
So that brand spankin' new extension just fubared your site? Akeeba will roll your site back and have you up and running again automatically!
So Many Features... You Just Have to Visit Akeeba's site!
While I could list all the features here, there's really no point in reinventing the wheel. Suffice it to say that Akeeba Backup is one extension that you MUST have on your Joomla site. Although the core extension is free, Please do support Nic by purchasing the Pro version, plus you'll get all the really good stuff when you do buy it.