I\'m using Twitter Bootstrap and some custom css (found here) to have dropdown menus open up on mouseover.
I am using the \"caret\" on a on the root menu items to show
As user2661940 said you can use glyphicons for Bootstrap 3 or you can also make your own class for every side. For example
.caret-right {
display: inline-block;
width: 0;
height: 0;
margin-left: 2px;
vertical-align: middle;
border-left: 4px solid;
border-bottom: 4px solid transparent;
border-top: 4px solid transparent;
}