On the File menu, click Page Setup. Click the Layout tab. Make sure
that Vertical alignment is set to "Top".
On the Format menu, click Paragraph. Click the Indents and Spacing
tab. Specify 0 pt for Space Before and Space After.
Note that if you are pressing ENTER twice to create spacing between
paragraphs, the actual spacing you get depends on the setting for Line
Spacing. For a number of reasons (see http://www.shaunakelly.com/word/concepts/rules_enterparagraphs/index.html),
you should press ENTER only once to create a new paragraph in Word
(and use Space After or Space Before whenever you need spacing between
paragraphs).