Keeping a backup of your website is a wonderful idea. It provides insurance against all types of setbacks, such as security compromises and inadvertently deleting your entire site (it happens).
We suggest backing up your site before you make changes each and every time. That way, if something goes awry, you have a fresh copy that you know is working. It might seem like a hassle, but the first time you use a backup, you're going to pat yourself on the back for having so much foresight.
If your hosting account has any databases, back them up first. This puts copies of your databases in a directory called
_db_backups so you can download them later.
For more information, see the Backing up a MySQL or MSSQL Database section of Backing up and Restoring MySQL or MSSQL Databases.
The easiest way to back up your website is with a File Transfer Protocol (FTP) client. This lets you connect your local computer to your hosting account and move files between them. To back up your website, you'll just copy all of the files from your hosting account to your local computer.
We recommend using FileZilla. For more information, see Move my website with FTP and FileZilla.
It's a good idea to keep these backups in a unique folder on your computer called something like
website backups. In that folder, create another folder with the date you created the backup, e.g.
feb2013 — put all of your files in here. This way, you can easily figure out when you created each backup in case you need to use one.
After backing up your hosting account, you can use the backup to restore it (more info).