Word is a Style-based application. You should learn about and use styles.
Importance of Styles in Word
Here is an example of changing the Body Text style to be single spaced within a paragraph and between paragraphs.
- Get to the Modify Style dialog (right-click on the style in the Styles Gallery or Styles Pane).
- Click on the Format button and...
- Pick Paragraph.
- Change the space before and space after settings to 0.
- Change the line spacing to single.
- Click OK to get out of the paragraph formatting dialog.
- Click OK to get out of the style modification dialog.
If you want this for all of your documents, check the choice for "New documents based on this template" before you click that last OK. (It is between the 2 and the 7 on the screenshot.)
If you are a regular Word user, I recommend, strongly that you learn some of its basics. It will save you a lot of angst and perhaps some hair.
Basic Concepts of Microsoft Word - from Shauna Kelly