Like Android 2.3, Ice Cream Sandwich offers you the possibility to take screenshots
using a combination of buttons, like: Volume Down + Power Button. When you press these buttons simultaneously you...
Volume down plus power button; hold for a couple seconds or your phone will lock
This does work by volume down and power , its really easy do now down load free or buy a app
Why doesn't this option work for me? (power+volume down)
Doesn't work for me either i trued even holding it down but screen just locks