I think it's good to analyze AFTER the fact. Like, why did things happen the way they did? After the end of every one of my flings/relationships, I always try to pull a lesson out of it. (stuff like: don't talk on the phone, don't let her figure me out, make a move sooner, etc) Then I apply these to my next girl. Learning from your mistakes is good.
The type of analyzing that I think Jester was talking about is pre/during the relationship. Thinking about stuff like "she laughed once, but not twice and it was kinda forced... What's that mean?" It's bad for a few reasons:
1. Most little things don't mean jack. Girls will do totally random stuff, and they have mood changes every day... You can't predict what she's thinking all the time. You can sometimes get a good GENERAL idea, but this is more "gut level" than deductive. A good rule is if you have to ask "should I keep going with this girl?" you probably shouldn't be going with her.
2. The more you think about someone, the more you like them. This is why challenge works: you get her thinking about you, analyzing your actions, and she ends up obsessed. Be careful the same thing doesn't happen to you.
So yeah, if you're new, the best way to go is to NOT think about girls, period. Have fun when you're around them, then forget them immediately.