Create styles only in your templates. Don't create styles in your documentsthat's a recipe for confusion.
Don't use the "Update automatically" option on your styles. Update them manually.
Update styles only in the template.
Standardize style names across your templates so that every style name has a consistent meaning and usage.
If possible, avoid applying direct formatting on top of styles. Create further styles as necessary to achieve the same effect as the direct formatting would.
Redefine the Normal Style
Why can't I redefine the Normal style by example like all the other styles?
I don't know, but it sure is annoying. Perhaps it's because so many other styles are based on the Normal style; any change you make to the Normal style cascades down to each of the other styles based on it.
Here's how to redefine the Normal style:
In Word 2003 and Word XP, choose Format » Styles and Formatting, right-click the Normal item in the Styles and Formatting pane, click the Modify button, and work in the Modify Style dialog box.
In Word 2000, choose Format » Style to display the Style dialog box. Click the Normal item in the Styles list, click the Modify button, and work in the Modify Style dialog box.
You can quickly access the Style drop-down listbox on the Formatting toolbar or the Style dialog box by pressing Ctrl+Shift+S. In Word 2003 and Word XP, press this key combination once to select the Style drop-down listbox if it's displayed, or to display the Style dialog box if the Styles drop-down list is not displayed. In Word 2000, press it once to select the Style dialog box.