jQuery .find() gets all the descendants of each element in the current set of matched elements, filtered by a selector; Also check jQuery .children() if you need to get only first level of depth;

js:

$('ul').find('li.target')
    .css('background-color', 'yellow')
    .append(' <span class="label label-info">.target</span>');​

html:

<ul>
<li>list item</li>
<li>list item
<ul>
<li>list item</li>
<li class="target">list item with target class</li>
<li>list item</li>
</ul>
</li>
<li class="target">list item with target class</li>
<li>list item</li>
<li>list item
<ul>
<li>list item</li>
<li class="target">list item with target class</li>
<li>list item</li>
</ul>
</li>
<li>list item</li>
<li class="target">list item with target class</li>
</ul>​