Creating bootable USB of fedora is really simple and easy , you can use that USB to install fedora in other computer or just use as it is , but if you are using live USB you cannot save your work in USB you have to save it somewhere else in safe place , because this is not a persistence usb install this is live install
Download : Fedora
Download : Unetbootin
Demonstrated using windows 8
and fedora 17 as live ISO
It require at least 4GB of USB ( 8 GB recommended )
Steps :
Format your USB drive First
Open unetbootin
Choose the correct USB drive
it will take upto 10 to 15 minutes depend on your system
wait until it finish copying files
After that just choose USB as your first boot device and boot with USB
you can use as live USB or you can use this usb key to install fedora its depend on your need
have fun with fedora !