These are usually displayed in alphabetical order. What this means is that you can create categories for websites, such as one for fan music sites or a separate folder devoted to your favorite hobby. Figure out where you want to go, and then create folders for every web activity you can think of. Folders produce little submenus on your bookmark screen, and you can even put folders inside of folders depending on how specific you want to be inside a certain category of interest. Well, that's pretty subjective.
Tastes obviously vary.
You use these most of all, so having an easily-accessible search engine folder is essential. Some of the newer browsers allow you to put a limited number of sites directly on a toolbar in the browser itself. This is better, and if you have Netscape 4 or IE 4, then it's preferable to put your favorite engine there for easy access. But you still should have a separate folder just for all the various search engines. Some are much better at finding things than others.