Ok, so everyone has talked about the chess game from book 1 as a possible hint at whats to come but how about the troll fight. I was rereading the book and it occured to me that this is when harry, rom and hermoine became friends so this may be important in the future books. Just a thought.
The troll fight basically like this:
Hermoine was trapped and ron and harry came to help her. Harry tries first and is basically stuck, so ron comes to the rescue.