A great way to find great locations to hunt duck is to search the internet for local guides.  Once you find one that is well respected check to see what area they concentrate their guiding on.  If a duck hunting guide is wont to hunt a certain area and is dependent on that area for his paycheck, odds are that area holds ducks.  Obviously you aren't likely to compete very well against that guide on the same lake, slough or river, but odds are there are several places within a 20 minute drive of their focus area.  Use this information to go out and scout with your own eyes.  You will be surprised at what is out there.

What are your experiences using duck guides to find high quality hunting spots?