This is a good article about the
wizard pattern http://ui-patterns.com/patterns/Wizard
The best is your third option, to have
Back buttons at the bottom right, because the user will commonly use them, he will mainly use the
Next button, and he will use the
Back button if he forgot something or want to check something. The
Cancel button should be at the bottom left because it's intended as the exception (i.e. the user wants to cancel the process).
download bmml source – Wireframes created with Balsamiq Mockups
It's very important to have the cancel button; imagine that you have a wizard with multiple steps, and you don't have the cancel button, and want to go back to where you started, then you have to click all the way back through clicking the
Back buttons several times, which is horrible experience for the user.