As mentioned in a previous post, Google penalizes sites for duplicate content. One way of solving this is modifying the robots.txt file. Daily Blog Tips describes another way to prevent Google from finding duplicate content on your site: by using excerpts:

In order to make sure that you are not incurring any penalty for duplicated content you should make all those pages display only post excerpts instead of full posts. You could even display post excerpts on the Homepage…

This method involves modifying the theme files so that only specific pages will display excerpts.

Use Post Excerpts Everywhere>>