German fluent speakers?

Hello! Well I've been currently taking German cles and it has become really difficult to remember all of those "Der" and "Die" and "Das" My teacher told me that there was a little clue in the en of the words that will give you a clue, but I dont see her anymore and I dont know anyone who speaks German. Can you please tell me what she was talking about???? (I know it wont apply to all the words but at least to most of them, I guess) Thanks :)