How to reset Launchpad ordering in OS X Yosemite?
Enter this line in the console:

defaults -currentHost write com.apple.dock ResetLaunchPad -bool true; killall Dock


Removing the db doesn't seem to do the trick any more. So this two steps are necessary to reset the Launchpad in Yosemite:


  
  rm ~/Library/Application\ Support/Dock/*.db ; killall Dock
  defaults write com.apple.dock ResetLaunchPad -bool true; killall Dock