This question was posted in response to the following article: http://help.adobe.com/en_US/indesign/cs/using/WSa285fff53dea4f8617383751001ea8cb3f-6d98a.h tml
Speaking as a complete newbie, I just got past a very rudimentary problem with justification. The dialog has no effect unless you've selected TEXT. I was selecting pages and seeing no effect. But then, after two days, I realized I needed to select the Text tool, click in some text, and then use Edit|Select All, or the shortcut key for this.
A much better way to handle justification is to set it as part of the Paragraph Style assigned to the text. It's in the Indents andSpacing section of the style definition dialog.