Compliments are always nice, but only when exercised with moderation and sincerity.
Other than that, rather than telling her something that makes her feel good, show her a good time and that will mean much more than words. The key to making a woman feel special is a gesture uniquely shared by the two of you. Such is the very essence of romance itself.
A night spent dancing in the moonlight, an orchid for guy Fawkes day, or even a shared movie night when you make time to be with her especially. Once all I did was toss her a bag of heart shaped dove chocolates passing between classes. But try to rerserve any deeper gestures until after you've been in a relationship for a while, otherwise it lacks credibility and sends the exact opposite message.
-CyranoDeBergerac