I missed my chance. But how can I improve next time?

About two weeks ago, I went to a conference/career fair and they had this medium-size dance party (no alcohol, just dancing). I don’t know how to dance, but my female friends where teaching me how to dance. Anyway, I saw this beautiful short girl standing in the corner by herself, just observing the crowd. She didn’t look like a weirdo, she looked confident. Arms crossed, standing up straight, etc. Now, before I go any further I’ll describe myself. I’m pretty shy and reserved guy, but I can get out of my comfort zone with many people. I also have no game with women. Never got a girl’s number in high school (still haven’t gotten a girls number….), nor have I ever had a female friend. So, as you can guessed I was afraid to approach this girl. All my friends were telling me to ask her to dance, but like I said before, I don’t know how to and I’ll make a fool out of myself. So, I’m just quietly looking at her every few minutes. Within a 10 minute span, three guys approach her. They talk and seem to seduce her, but it isn’t working. They leave like the ones before them. That made me even more afraid to approach her, she definitely knows she’s attractive with guys approaching her, what difference I’m going to make without being rejected like the previous guys? After telling myself to stop being a pussy, I decide to go talk to her. I don’t what I’m going to say to her, but I’m just going to talk to her. Unfortunately, by the time I decided to man up, she left. I spent like 15 minutes walking around and trying to find her, but couldn’t. I felt angry with myself because I didn’t take my chance. Later, one of my female friends told me that she was proud that I searched for the girl in order to talk to her.

Now,

1. What could I have said to make myself stand out? That I wouldn’t do the walk of shame after 1 minute of approaching her. How could she have remembered me?

2. The conference is held every year and I’m certain that I will go to next year’s conference which will most likely have a dance. I hope to see her there and if I do, what are some pointers to approach her? I don’t wanna say, “Hey, I remember you. I saw you at last year’s conference.” That sounds kind of creepy.