Take Preferences. Please. Nearly every Mac app of significance creates preference files on your Mac, usually found in the user Library > Preferences folder.
Every now and again things go wonky wrong, and deleting or editing a Plist file in the Preferences folder can bring back the magic.
Any decent text editor can read a Preference file, but only PrefEdit lets you manage what’s under the hood. Plist means Property List files which store user preference settings. Plist manifest files contain descriptions for Preferences.
PrefEdit isn’t for the faint of heart. You’re required to have a bona fide Mac geek gene in your possession. However, nothing is better at editing the preferences database in OS X, including all the user settings. PrefEdit also lets you browse Plist file, and edit file contents.
Apple has many hidden features and preferences in OS X and Mac apps, too. For those, I’ve found it better and faster to use Onyx, Maintenance, or Deeper, all free.