Or you can choose Security options to erase your data 1, 3, or 7 times to ensure no one can recover your files.Assuming you want to clean install (follow these steps; I just did this a few hours ago).
1. BACK UP ANYTHING IMPORTANT!!!! I forgot to backup my music (luckily I found a free program to copy all my music back from my iPod or else I was screwed!) BACK IT UP NOW! If you don't want to do a Time Machine file, then just copy your files that you want (E.G. iTunes Folder, important documents).
2. Restart/boot-up your computer. Press and hold Command+R until a menu comes up asking you what language you want. Choose what Language you want and hit continue.
3. Choose "Disk Ultility". Choose your Mac OS X partition, choose the "Erase" tab, then choose "Erase"
4. Exit out of the Disk Utility and Choose "Reinstall Lion".
5. Follow the instructions given.
Hope I helped!
Restoring from TM would pretty much put you right back where you are now. A true "clean" install is a fresh OS install followed by manual reinstall of all apps and settings.But obviously i don't want to lose my files, so I could just restore from time machine, but would restoring from time machine defeat the object of a clean install, since the backup is pre-clean install, and it'll be putting those files back?
Equally i don't want to have to back up my files and restore them manually because that was one of the things i disliked most about windows.