My friends have learned to come to me for advice and not sympathy/empathy. I'm awful at comforting someone. I have a really good habit of making things worse when I'm just trying to make them feel better.
For instance - I was a bridesmaid at my friends wedding recently, and she was nervous about tripping and falling...I didn't know how to make her feel better, so I tried to be funny and say, "Yeah! And they'd ALL be looking at you!" Needless to say, that didn't work too well.
I try to keep my mouth shut, let them rant/cry, and tell them if they need something, to let me know and I'll help in anyway I can. Other than that, I'm just not much help.