Baby Photography

YAY! YAY! YAY!
I have two baby photo sessions this weekend! I am so excited! And freaked out!
I love babies and I can't wait to photograph them!  However, I'm nervous that what I have in mind for these photos is different from what the parents have in mind... I'm also nervous because I've heard so many people say that babies are really hard to photograph... Is there something that I'm not considering?