There are bazillions of threads on this topic.
Unless you think you're better at installing Lion than Apple engineers are, or have a specific problem that can be solved by erasing your hard drive and "copying" things back, why would you do this?
A clean install is no longer a supported installation method. Read up on the various ways to accomplish it, and make sure you have an adequate backup. You'll need it. If you are not very familiar with the intricacies of Mac software, I suggest you do a TM backup or make a clone. Make sure they have all the info you want and need. Then proceed to reformat your boot drive and migrate your user applications and data back using Setup Assistant. If you don't know what these things mean, I suggest you just install per Apple's instructions.
Good luck
Rob