Creating Conflict from Characters

I am often asked (by people who want to write) how I come up with all these different plot twists and conflicts, so I thought I'd do a quick post on it.  I have no idea about other writers, but I get most of my conflicts from characters.  For instance: Yesterday I was working on the basic plot for an upcoming book.  I listened to music, paced the floor, and let the characters take over.  Now this book is the third installment in the Witch-Game series.  Maybe I should give you the basic idea of what the book is about before telling you what the characters were doing in my head.

My three main characters have been best friends since Kindergarten, really tight.  There are two boys and a girl.  One of the boys falls in love with the girl, and it looks like they might even get married someday.  Then tragedy strikes.  His brother dies, and he's so torn up about it that he leaves town without even saying goodbye to the girl or his other friend.  Now he's back.  He's working for a task force that stops witches from playing these dangerous games, and he has a partner with him.  Her name is Jordan, she's cute, and she has a huge crush on him.  At some point the girl he was in love with is in danger so he leaves Jordan with her to protect her. 

The scene that played out in my head took place in the girl's (we'll call her Nina for now) bedroom.  Jordan picks up a picture of Nina, the other friend, and the guy (we'll call him Jon for now) they both like.  Jordan says: I've never seen that smile before.  Nina yanks the photo away and says something like: That's because he was happy here with us.

I can see a catfight coming. 

So that's how I create conflict from characters.  Although I get the basic conflicts from the main story idea, a great deal comes from the characters.  I look at each character closely to see what they want and who stands in their way.  I look at their childhood traumas, their present problems, and the conflicts are born from that. 

If anyone has anything to add or a different method, I'd love to hear it, and I'm sure other people would too.