Preventing Duplicate Content Issues.

Google likes good quality original content, if you have copied content you will get penalised for it. If you are rewritting content to fool the search engines,  remember that they may just count key words and form a pattern going on.

i.e you may have changed a few words around but you still have the exact amount of the one same word.

Please use this tool to make sure you havent been given dodgy content.

http://www.copyscape.com/

If you are quoted news articles, google have stipulated in there guidelines that a small portion is acceptable.  You could keep it to 5 lines to be safe.

You may have duplicate content issues, especially on your home page, check canonical page.

Do not use a robots.txt or meta tags to block duplicate content.

Should I block duplicate pages using robots.txt?