To make a bootable USB installer, format a USB to OSX Extended (journaled) naming it Untitled, download the developer preview...
Then type the following on terminal:
sudo /Applications/Install\ 10.12\ Developer\ Preview.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ 10.12\ Developer\ Preview.app --nointeraction
Cheers
Then type the following on terminal:
sudo /Applications/Install\ 10.12\ Developer\ Preview.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ 10.12\ Developer\ Preview.app --nointeraction
Cheers