If you want to change line spacing for the entire document, press "Ctrl-A" to quickly select all text. On the Home tab, click the "Line and Paragraph Spacing" button found in the Paragraph group.

You can also set the spacing between paragraphs in a single document or in the template. By default, Word 2011 inserts 1 1/2 spaces between paragraphs.

To change the spacing, choose Paragraph from the Format dropdown (Figure B). In the resulting dialog, check the Don’t Add Space Between Paragraphs Of The Same Style option in the Spacing section ...