Hello there,
Can you tell me please that how to check duplicate content?
I am waiting for your positive responses.
Thanks in advance.

IF you have created some inspirational sentences or quote for which you wan to get notification if someone else used in his website, you can set Google alert for those sentence and if Google would find out your content, it would notify you.

Another way to check duplicate content is by using two websites, Copyscape.com which checks the content of the URL and Articlechecker.com in which you can post your article or piece of content to check for duplicate.

You can find all duplicate content in copyscape.com for your website. You just need to put your website Url. Another one is dustball.com/cs/plagiarism.checker/.

After Panda update, Google will take care of the duplicate content.

There are lots of tools that can check duplicate content.

you can also check the duplicate content using google. copy the content and paste that into google search if google highlight the your same content in search. then its duplicate.

Duplicate Content is the main reason of penalization by search engine when you are submitting the content on any site you must check the content that is duplicate or copied from any where. On internet many tools are available that checks the content whether it is duplicate or not. you can use Copyscape, articlechecker and many tools available on Internet. Thanks 

I prefer to check by Google webmaster tool only and the procedure is same as antony05 suggested. And other option is copyscape which also best for checking duplication but I think it is paid not free.

If you have published the content and have the url then you can check that on copyscape, which is the best method to check the duplicate content issue.

You can use copyscape.com to check the duplicate content by placing the url in it.