Using Robots.txt File to Stop Duplicate Content

[Rhett]

In order to avoid duplicate content on our WP sites I found where some recommend using the robots.txt file. Does that sound right? I found the following code that one person recommends to stop duplicate content:

User-agent: *

Sitemap: http://yourblog.com/sitemap.xml
Allow: /wp-content/uploads/
Disallow: /cgi-bin/
Disallow: /wp-admin/
Disallow: /wp-login.php
Disallow: /wp-includes/
Disallow: /wp-content/
Disallow: /wp-content/plugins/
Disallow: /wp-content/cache/
Disallow: /wp-content/themes/
Disallow: /*?*
Disallow: /*?
Disallow: /archives/
Disallow: /feed/
Disallow: /comments/feed/
Disallow: /comments
Disallow: /feed/$
Disallow: /*/feed/$
Disallow: /*/feed/rss/$
Disallow: /*/trackback/$
Disallow: /*/*/feed/$
Disallow: /*/*/feed/rss/$
Disallow: /*/*/trackback/$
Disallow: /*/*/*/feed/$
Disallow: /*/*/*/feed/rss/$
Disallow: /*/*/*/trackback/$
Disallow: /tmp/
Disallow: /tag/
Disallow: /category/
Disallow: /category/*/*
Disallow: /author/
Disallow: /wp-*
Disallow: /tag/
Disallow: /*.js$
Disallow: /*.inc$
Disallow: /*.css$
Disallow: /*.gz$
Disallow: /*.wmv$
Disallow: /*.cgi$
Disallow: /*.php$
Disallow: /trackback/
Disallow: */trackback
Disallow: */feed
Disallow: */comments
Disallow: /*?*
Disallow: /*?
Disallow: /z/j/
Disallow: /z/c/
Disallow: /stats/
Disallow: */comment-page/
Disallow: /*/feed/
Disallow: /*feed/

This is just one example of a robots.txt file. It seems as if everyone has their own version and I have no idea which is best.

I definitely have a duplicate content issue on my site. WebMaster Tools says I have 595 URLs in my sitemap but now I only have 88 of them indexed. The number of pages indexed keeps going down.

I have the tag.php file set for excerpt and I'm in the process of writing excerpts for all of my posts. That should take care of the tags issues but isn't it possible that duplicate content can also appear through feeds, archives, etc.?

Any advice would be greatly appreciated. It seems as if my site is dying right before my very eyes.

Thanks.