Articles Website Duplicate Articles

Refer the content to the page, eg. source: www.example.com

This way you got outbound links and hopefully you'll get some inbound links back as its a chain effect if someone saw that article of yours and want to link it to their own website they will link using this method and put your URL as source.

There are many forms of SEO.

1. WWW and NON WWW, if you dont choose one or the other search engine will have your site as duplicate. one under www.example.com and the other example.com
so if your site gets 8/10 ranking it will now be 4/10 for www and 4/10 for non www

2. keywords have to match the text as much as possible, irrelevant keyword and text will result in bad ranking.

3. Inbound/outbound links, list your site on as many websites as possible, there are many free listings.
http://www.alexa.com/ 
www.dmoz.org
www.opendirectorys.com
http://www.google.com/dirhp

4. Have you listed your websites with all the search engine? google, yahoo, bing, etc etc? do you have a sitemap? if no please search on how to make a simple sitemap which will help the search engine robot find things alot faster.

5. Do you have a robot file? this also helps
www.outfront.net/tutorials_02/adv_tech/robots.htm

Many more SEO but those are the ones on top of my head and most important.

With Google's latest update you might find it a bit harder.

The simple (and white hat) answer it to not let people submit duplicate content, so your website becomes an original source of useful information.

Websites can perform with duplicate content. It tends to be the ones that Google thinks contain the original copy (unless they've been slam dunked with the new algo).

If you think you're already suffering from this try using copyscape  (http://www.copyscape.com) to detect the duplicate content. Warn your article submitters to not submit articles that already haven been posted elsewhere and possibly apply moderation before posting the articles to your website.