Fontawesome for icons is … awesome.  The easiest way to use it is their CDN. It’s one less thing to serve from your hosting and, as it’s widely used, your site visitors may already have it cached in their browser (evidence here).

In WordPress, to use the fontawesome CDN without using a plugin, and to use the best practice enqueue method, add this to your (child) theme’s functions.php

 

add_action( 'wp_enqueue_scripts', 'prefix_enqueue_awesome' );
/**
* Register and load font awesome CSS files using a CDN.
*
* @link http://www.bootstrapcdn.com/#fontawesome
* @author FAT Media
*/
function prefix_enqueue_awesome() {
wp_enqueue_style( 'prefix-font-awesome', '//maxcdn.bootstrapcdn.com/font-awesome/4.3.0/css/font-awesome.min.css', array(), '4.3.0' );
}

Tip: Check the latest version number and change the URL + version number in the code above to be up-to-date.