This technique uses the Universal USB Installer, for more info or more help visit http://www.pendrivelinux.com/.

Insert a USB stick with at least 2GB of free space

Download the Universal USB Installer

Click 'Run' when prompted

If the security dialog appears, confirm by clicking 'Run'

Read the licence agreement and choose 'I Agree' to continue

Select Tails from the dropdown list

Click 'Browse' and open the downloaded ISO file

Choose the USB drive

Click 'Create'

Then safely remove the USB stick from the computer.