I tried for about a week to create a bootable liveUSB with Tails ... never did get it to work. I was able to set up the USB and the necessary reFIT/reFIND stuff, and have it all show up properly upon startup ... but then when I would select to boot from the thumb drive, it always gave me an error. So, now I'm just using a liveCD/DVD with Tails on it -- and a separate USB for important documents/keys/etc.