General Best Practices I learned from Using Joomla
1.) Make backups regularly.
2.) Use a strong password to secure your Joomla Administrator access.
3.) Use Powerful security extensions.
4.) Make sure you are using the latest version and extensions Joomla.
5.) Monitor your Joomla site.
6.) Delete extensions you are not going to use.
Joomla Security Best Practices
1.) Use a security key to log in to your Joomla Admin.
2.) Enable search engine friendly to help visitors find your site.
3.) Keep file/folder permission appropriate.