Home button or Sleep/Wake button not working properly? (Maybe you had some kind of iPhone misfortune involving water or a drop?) You're probably planning to take your phone in to get fixed; but in the mean time, Assistive Touch is a great work around to this problem:
To turn on Assistive Touch go to Settings>General>Accessibility>Assistive Touch and toggle Assistive Touch on.
A virtual Home button will now appear on your screen at all times. Press this button and you will bring up a screen like this:
Tapping Favorites will allow you to create your own custom gestures.
Tap Siri to use your phone's digital assistant.
Tap Home to return to the Homescreen.
And tap Device to bring up a whole new menu of options that allow yout to lock the screen orientation, rotate the screen, adjust the volume, mute or unmute your ringer:
Tapping More will bring up another menu that let you shake to undo, take a screenshot, bring up the multitasking bar, or use gestures.