The default table prefix for a wordpress install is ‘wp_’ – make it different! Any attacker attempting to access database tables will use the default naming convention first – don’t make it easier for them!
Changing the table prefix on an existing site is quite involved so employ this from the outsetwhen you’re running through the setup.
Should you wish to do this to an existing installation, the table_prefix variable can be found as shown below in the wpconfig.php file:
This article describes how to set WordPress AUTH KEY parameters in your wp-config.php file to secure your cookies. These will ensure that your authentication cookies are encrypted using unique random salts – Codeseekah has done a good write-up and explanation here.