Use Styles!

• The Importance of Styles in Microsoft Word
• Using Styles to Format Text

Your headings should use a heading style, perhaps one of the built-in ones modified to look the way you want. Why Use Word's Built-In Heading Styles? by Shauna Kelly

Your body text should use the Body Text style, or the Normal style or one that you want. You apply the style to the paragraph and then select it and press Ctrl+Spacebar to clear any direct formatting.