As your WordPress site is your online presence, you want to make sure you have a backup of all the key items. Those items are likely the custom file modifications, and the database. WordPress core, plugins, and themes could all be downloaded again if you needed to, which is why I consider them a nice to have in the backup process.
There are multiple ways to create backups of these files from manual, to plugin automation, to vendor provided solutions.
Manual: Who wants this? It is time consuming and a hassle to login to multuple locations, download files, and archive them.
WordPress Backup Plugins: These will automate the process and save you time and frustration.
- BackWPup (free plugin) – Can save to multiple locations such as directory, ftp, dropbox, amazon s3, etc.
- BackUpWordPress (free plugin) – Saves backup locally.
- BackupBuddy (paid plugin) – Can save to multiple locations such as directory, ftp, dropbox, rackspace cloud, amazon s3, etc.
- VaultPress (paid plugin + monthly service) – Does everything you want and provides the storage space as well so you don’t have to worry about where to backups are stored either.
Also note that some web providers / hosts perform backups on your behalf already, so you might want to investigate the built in options at a server and host level too.