Scroll to Top
Tapping the status bar where the clock and battery charge etc. is displayed will scroll to the top in most apps.
Swipe to Go Back
Swiping from left to right will take you back a screen.
Double-tap the Home button to view a list of the apps you have opened. Tap an app to switch to it, or drag it upwards to close it. Note that closing an app is only necessary if it stops responding.
Shake to Undo
Made a mistake whilst typing? Shake your iPhone to undo.
Swipe down from any home screen to use Spotlight to search for content on your iPhone.