from [[http://www.mactrast.com/2013/06/how-to-build-a-bootable-usb-installer-for-the-os-x-mavericks-developer-preview/]]\\
1. Show hidden files by opening ''/Applications/Utilities/Terminal.app'' and typing the following:
<code>
defaults write com.apple.finder AppleShowAllFiles TRUE
killall Finder
</code>
2. Right click ''Installer.app'' file and click ''Show Package Contents'', Open ''Contents'' folder, then look in ''SharedSupport'' folder. You will see **''InstallESD.dmg''**.\\
3. Mount **''InstallESD.dmg''**.\\
4. Copy the **''BaseSystem.dmg''** file out to somewhere convenient.\\
5. Do not mount **''BaseSystem.dmg''**. Just open **Disk Utility** and restore it to a flash drive.\\
6. When that’s done look in the flash drive you just restored to and go to ''/System/Installation/''. In that folder you will see a white icon with an arrow called ''Packages''. That’s a broken alias. Delete it.\\
7. Now go back to your **''InstallESD.dmg''** file. Inside is a folder weighing in at about 4.5GB called ''Packages''. Copy that folder onto the flash drive in place of where the alias was.\\
8. Go ahead and hide the hidden folders again by going back to the Terminal and typing:
<code>
defaults write com.apple.finder AppleShowAllFiles FALSE
killall Finder
</code>
9. Done. Boot from the flash drive and get to work.

[[http://osxdaily.com/2013/06/12/make-boot-os-x-mavericks-usb-install-drive/]] says that you have to use **Disk Utility** to format the USB stick to ''1 Partition'' with ''Options -> GUID''