You don't really need any classes with some clever usage of the selectors :P
I set up a fiddle with an example, here's the code:
HTML:
<nav>
<ul>
<li><a href="#">HOME</a></li>
<li>
<a href="#">OFFERS</a>
<ul>
<li>
<a href="#">NEW</a>
<ul>
<li>YAY!</li>
</ul>
</li>
</ul>
</li>
<li><a href="#">SETTINGS</a></li>
<li><a href="#">TV's</a></li>
<li><a href="#">COMPUTERS</a></li>
<li><a href="#">RICE</a></li>
</ul>
</nav>
As you see, not a single class/id was needed :P The element "OFFERS" is the only one with a drop-down menu, and inside that menu, the element "NEW" has another one.
CSS:
li > ul { display: none; }
li li { margin-left: 10px; }
The first style is the important one. At first, we want our submenus to be hidden. The other style is just for the sake of clarity.
jQuery:
$("nav ul li").hover(function(){
if ($("> ul", this).length > 0) {
$("> ul", this).show();
}
}, function(){
if ($("> ul", this).length > 0) {
$("> ul", this).hide();
}
});
Yup, as simple as that :) When we hover a menu element, we check if it has any ul direct children, if it does, we show them. When we leave the menu element, we check again if it has any ul direct children, and if it does, we hide them.
Of course, you'll need to style this up, and make sure your clear any float inside any li.