Twitter user Jaroneko published some instructions on how to create a bootable USB for OS X 10.10 the other day.
This is a revised edition tweaked by me to address a couple of the errors terminal was spewing out in response to Jaroneko's instructions, as well as improving the clarity of the process with exercising the verbose option.
If OS X 10.10 Developer Preview.app is in /Downloads:
- defaults write com.apple.finder AppleShowAllFiles TRUE
- killall Finder
- sudo hdiutil attach ~/Downloads/Install\ OS\ X\ 10.10\ Developer\ Preview.app/Contents/SharedSupport/InstallESD.dmg
- diskutil list (Find the /dev/disk corrosponding to your USB stick).