Basically, when dealing with non-fiction topics like business or security or Information Technology or any other factual topic, there is really only so many ways you can write the facts using the English language. For example in business, when writing about forming a company you have a certain "checklist" you go through when forming a company, things you have to do. Things to take in to consideration etc. There is really only a few ways to describe it. Then when 400 other people wrote 2000 other articles about that subject, you can't write it without technically write the same way as someone else. And no, the answer is not "then don't write it", because when you have let's say a business blog, you really have to have that base of articles so that your readers can get through the entire process that you are trying to describe on your site and not have to jump to other sites to fill in the blanks.
So, again, taking that into consideration, how do you write articles without plagiarizing when everything has essentially been said about the topic at hand?