Not happy with being Jailbroken? Want to send your phone in for a warranty fix? Let's get her back to stock shall we?
Step 1: Plug in iPhone 4S
Step 2: (Reccomended but not necessary) Backup
Step 3: Press Restore
Step 4: Wait.
Step 5: Follow Apple's easy to follow instructions.
Step 6: Enjoy your stock iPhone!
A simple task but I still get questions about it.
Hope that helped!