Duplicate content is a issue faced by any website, not just those driven by WordPress. But, out of the box, WordPress tends create duplicate content issues with features like
- Archives
- Tags
- Search
Depending how much of your post you display on your blog home page, your home page might be doing some damage too.
One way to avoid this, is to leverage the robots meta tag. By giving search engines the noindex instruction, we are essentially instructing them not to index this page, and not to consider it when comparing pages for duplicate content.
The quickest way to do this, is in your WordPress theme's header.php file. Anywhere within the head section (between the opening and closing <head> tags), you can drop in the following code:
<?php if (is_home() || is_archive() || is_search())
echo "<meta=\"robots\" content=\"noindex\" />\n"; ?>