firstly, do not take the advice of the first two posters - unless you don't want to see this chick again.
Just say that to determine whether i like a person or whether i think a girl is 'hot' i have to get to know their total being as a person and not just the outside of their shell -- she'll love you for saying this and might give you a big kiss right then and there!
This will add mystery to your persona and it will show her that you are not easily impressed and that she would have to prove herself to you.
She will then ask you more questions - be prepared - but give her only tidbits at a time -- like your confuscious or something - depart your words of wisdom but only sparingly. This, my man, is how you keep her interest level high -- keep her coming for more.
Never tell a woman someone looks better than them -- just say that they have enough beauty to hold their own independent of others.
If you say what the first two posters suggest - be ready for a slap and then "I hate you" after that. If you say this Just put your hands on your side ready to block the slap karate style