Answer by Kenny for Adding jQuery to Magento

Best is to use the content delivery network which will be better in performance/speed for your website.

I mostly just open up template/page/html/head.phtml and right before

<?php echo $this->getCssJsHtml() ?>
<?php echo $this->getChildHtml() ?>

I add:

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>

Also make sure you run the jQuery.noConflict() method and always use the full jQuery name instead of the $ (dollar sign) to avoid conflicts with prototype ;)