When I first heard the term "due diligence", I was confused. The more I studied and examined the concept though, the less confusing the term became.
In general, due diligence deals with being as thorough as you can when tackling an issue. In every profession, there's a basic requirement that you work hard to make discoveries and evaluations about simple and complex issues. As an attorney, I'm often confronted with cases that require thoroughness and details in order to be successful.
I've written several times about the need to exercise diligence when you're reviewing personal or business contracts.
The same caution goes for business and even individuals you're doing business with. It's important to discover, before the eventual breakdown, what "skeletons" the other party is hiding.
For instance, if you're a business, negotiating with another business for products or services, it's essential that you "fish" for information on the internet.
We're lucky in Oklahoma, because we have one of the finest state court systems in the country. When you visit the Oklahoma State Courts Network or Oklahoma District Court Records, you're granted access to enormous amounts of information about parties.
With these resources, and a number of other private ones, it's quite simple to gather as much "competitive intelligence" about your opposition/ally. Use this knowledge to protect yourself from future problems.