Do not say "you are beautiful". Calm down. You're making too much of this. I don't know why people are saying "Girls like guys with confidence.." and all of that. It depends on the girl. It is your call. There is no special trick or spell to get it right. Her sense of humor, taste, and personality all come in to play. You need to know what is up before you try to go with it. Don't approach her in a special way, or use special words. Just say what you need to say. It is not an art, you do not need to be a "pimp". Just relax.