I've mentioned a number of times the importance of using Styles in Microsoft Word. It helps ensure your formatting is the same across your document, it makes it easier to change your formatting, and it automatically builds a table of contents for you. If that isn't enough to convince you to use Styles, let me add another reason: it makes document navigation easier.
If you have a document that is several pages long with multiple sections - briefs come to mind - it can be daunting at times to find the section you want to review. However, it you format each heading using a Style, then the navigation pane will allow you to easily jump from to the section you want to review.
To open the navigation tab, you can either go to the Home tab and click on the "Find" button or just press Ctrl+f.
This will open a pane on the left hand side that allows you to search your document for a keyword. If you click on the navigation pane button, it will pull up a table of contents. I've circled the correct button below.
Clicking on any of the labels in the pane will take you directly to that section of your document.
As if that wasn't useful enough, you can actually reorganize entire sections in this pane. Let's suppose you really meant to have the State of the Case after the Statement of Facts. Simply click and drag the Statement of the Case label below Statement of Facts. Doing so will move the entire section in your document. That includes both the heading as well as all of the body text in that section. This method of moving sections is much more efficient and less frustrating than trying to do it in the body of the document itself.
None of these features work unless you have assigned each heading a table of content level, which is most easily done through the use of Styles. Yet another reason to start using Styles.