Home button is not working properly and iPhone 4s is under warranty, what to do?

Take it to Apple or an Apple Authorized service provider which you can look up on the Apple web site. They will check it out and if it is covered under your warranty, they'll fix it for you. If you have anyone else try to fix it for you, you will void your warranty. Only use Apple or an Apple Authorized service center (and any place claiming to be apple authorized but not listed on the web site is NOT apple authorized).