As you observe turbulence can strike without warning and be extremely violent.
I would say that if your in the aisle grab on to an armrest to steady yourself and try and get into a seat (any one!) and strap in. If its a full cabin and its getting really choppy then I would say, get down on your knees and hold onto that armrest with both hands - make sure you keep an eye out for anything falling from the overhead bins and/or loose trolleys. You might in extreme circumstances consider sitting down on the lap of another pax and asking them to hold on to you - Not ideal for the other passenger
(don't choose the UM or frail old grandmother) but then neither is concussion.
