You have to add the code when DOM is ready and your missing the #
for an id selector, try something like this:
<script>
$(function(){//When DOM is ready
$('#a_tip').qtip({
content: 'This is an active list element',
show: 'mouseover',
hide: 'mouseout'
});
});
</script>
Also add the following style to make the qTip appear:
<style>
#a_tip{
display:inline
}
</style>