PHP function to load jQuery in WordPress footer

Loading stuff on the footer, rather than in the header, makes your site load faster, because you move the blocking HTTP calls further down the page.

A word of caution: make sure that all your plugins work after this.

function load_jquery() {
  // Only use this method when not in wp-admin
  if (!is_admin()) {
    // Discover the correct protocol to use
    $protocol = 'http:';
 
    if ($_SERVER['HTTPS']=='on') {
      $protocol = 'https:';
    }
 
    // Settings for the script, change these to your liking
    // jQuery version you want
    $jquery_version = '2.0.3';
    // The url you want it from. Default to Google CDN
    $jquery_url = $protocol . '//ajax.googleapis.com/ajax/libs/jquery/' . $jquery_version . '/jquery.min.js';
    // Load in footer
    $footer_load = true;
 
    // Deregister the original version of jQuery
    wp_deregister_script('jquery');
    // Register the new version
    wp_register_script('jquery', $jquery_url, false, $jquery_version, $footer_load);
    // Add it back into the queue
    wp_enqueue_script('jquery');
  }
}
 
add_action('template_redirect', 'load_jquery');
add_action('wp_enqueue_scripts', 'my_scripts_method');

That goes into your themes functions.php file.

Further reading