There's way more to Sec. 508 compliance such as compatibility with screen readers, color choices in case users are color blind and users that access your content using alternate input methods.
For interaction compliance the rules can be summed up as: Can relevant info be obtained without having to explicitly use a mouse movement (hover) or click (pop-up menus, disclosure triangles)? Or can text descriptions of image-based content be accessed by accessibility tools e.g. describing the current value for a dynamically generated object such as a progress bar.
You can control tab-order in HTML elements, not just HTML forms. Don't rely on a hover event to show additional info. This is also useful for touch-based interface devices that have no "hover" concept.
Can font sizes be increased without breaking the overall layout? Some users may simply be hard of sight and use larger font settings than you are designing with.
There are tons of free resources describing the various compliance levels you can work towards, tools to test your content for compliance and instructions on how to turn on Universal Access software built into modern OSes.