Try triple-clicking the home button and see if that turns VoiceOver off, and if it does you can then change what a triple-click does via Settings > General > Accessibility > Triple-Click Home.
If that doesn't turn it off then you can either turn it off directly on the iPad (you need to use a tap-to-select and then double-tap to activate/type process and 3 fingered scrolling i.e. tap to highlight the digit of your passcode and then double-tap to type it) to go into Settings > General > Accessibility and turn VoiceOver 'off', or you can do it by connecting to your computer's iTunes : http://support.apple.com/kb/HT4064