Sunnis and shites,how do you tell the difference?

how do arabs tell the difference between a sunni and a shite before killing each other,i asked a similar question about how the irish catholics and protestants could tell the difference before they killed each other,but recieved a violition notice before i could get an answer.so trying again,i need to know so that i may be able to stay out of their way so as not to become "collateral damage" when they meet.sunni's shites,catholics and protestants or any other religious people please help me how to keep out of your way.