There are a huge number of Joomla extensions, and it is hard to choose the best extension meets your needs.
I will try to help in this area, by publishing reviews for the extensions focusing on features, pros and cons, and the purposes of each extension.

Its very important to backup your Joomla! powered website, this is a life saver if your hosting account is  hacked or deleted for any reason.

Also, it is important when you want to transfer/migrate or copy your website to another server.

Akeeba backup is the best extension to accomplish this task, and this is my review after using this excellent extension many times...