I'm thinking of submitting some articles to some sites to get some backlinks for my site. I know people do this a lot, but wouldn't that mean duplicate content if the other site has the same article as on mine?
Do not submit articles that you have already published on your own site. Write new articles, spin them in order to get 50-100 "unique content" versions and then submit to article directories.
ahhh, i see... so there is little merit in those services that submit an article to 50+ websites? since 49 of those will be duplicates anyway?
another question, when rewriting an article, does all of it need to be rewritten? i.e. no one sentence is left the same?
yes...do not use the content of your website for the article of your Article Submission or Press Release...Be careful in Any Duplicate Content...duplicate content is very big issue....
Duplicate content in articles is not penalized as duplicate contents on websites. It would be better to have unique contents in different articles sites, but duplicate content on different article sites will still benefit you.
Even if you spin / rewrite each article, your articles will still be copied by others so don't worry all that much about duplicate content when you are doing article submissions. Irrespective of what you do, there will be duplicate content.
Try to rewrite at least 40-50-60% of it. First & Last paragraph should be rewritten and you will need a new title. Check if it's unique enough here: http://www.copyscape.com/
They use software to do that fast. There are quite a few article directory submitters around. 75%? Basically it's a completely new article, not a rewritten article