How to add CSS in drupal?

<?php
 // Repeat this line for every CSS file added. 
drupal_add_css(path_to_theme() . '/example.css', 'theme', 'all', TRUE); 
 // Reassemble the $styles snippet to include the new files. 
$styles = drupal_get_css(); 
?>

Enjoy Drupaling.

Cheers!