I Fail At Flirting

I remember a few months ago, when I decided to flirt with one of the boys at my school that I had a crush on. So I went up to him, twirling my hair in what I thought was 'girly', and he just stared at me like Do you have leeches in your hair? I decided to try to talk to him, but I didn't know what to say, so we just stared at each other in a non-flirtatious way, like robots, until he broke the silence.
"Don't you have to go to class?" he was asking, and I just stood there, feeling like a loser/stranger/weirdo. But, of course, the truth was that I DID have to go to class, and I was late for it. So I had to rush away, and get scolded from my teacher for being two seconds late. (but that isn't the problem)
I need some lessons for flirting!! Seriously, I do. Can someone please help me?? Today I tried flirting with the same boy I did a few months ago, and I failed even worse. I picked a time when school was nearly over and it was dismissal time. But there were too many people everywhere, and he couldn't even hear me. The worst thing was, I just tripped on my face as soon as I went near him, and all my stuff flew everywhere.
I don't have a dating life. *sighs* but thanks for reading my story! I like to flirt, but when I actually flirt, then... a disaster happens. Oh well, can you add some tips in the comments section at least?