In the USA most commands for an unplanned emergency are "heads down stay down, heads down stay down." Once the exits have been assessed then the evac commands begin which are "open seat belts get out, come this way, leave everything, jump jump" Evac command from the flight deck is "Get Out", if nothing from the flight deck the cabin crew can initiate an evacuation. In a planned evacuation the only difference is "Brace brace brace" just prior to landing. USA does not use NITS but instead uses NTSB, TEST or TESTS depending on the airline.