If you REALLY want to go to a school, don't meet up with them ahead of time. I did that and ended up getting burned, because during the actual interview a few months later we had nothing to talk about after already having met. My charm is very fleeting in nature, apparently. It can be VERY useful, and it helped me figure out where I wanted to apply and helped assure me that I was a pretty good applicant. But if you have your heart set on a place, meeting with them in advance can really only hurt you in my experience.
Then again I was very honest in our meeting, and did say that I was applying elsewhere and that the school was not top on my list at the moment. If you do meet with them, and you want to go there, make sure they know that... or something.