I recently jumped into a Magento project and, while setting everything up in my local environment, I encountered the following error when I hit the index page:

“There has been an error processing your request. Exception printing is disabled by default for security reasons.”

It took me a little over half an hour weeding through forum posts to find a fix.  It turns out a lot of users hit that generic error for a number of different reasons, so before the real debugging can begin, I needed to figure out what the real problem was, which turned out to be pretty simple.

If you hit that error, the first thing you should do is change errors/local.xml.sample to errors/local.xml and refresh your page.  Once that’s done, you should see a more detailed error message that points to the real problem.  In my case it was database permissions, which was easily fixed, but it could be something different for someone else.  Regardless, the win here is getting to a helpful error message that points to the real problem, which is what the XML file change allows.