dress differently for a day, pamper yourself - the guys you already know will also notice the change
if you're usually talkative/loud, try being quiet
and vice versa.
if you're a flirt, then tone it down and try being a little shy
and vice versa.
a new hairstyle would also be helpful
but what really works is if you just look at the guy you want to notice you, watch his eye, smile and look away. then try getting closer to him physically and strike up a conversation. it's not that hard
Wear decent, matching clothes. Wear matching hear-band,ribbons, footwear, bangles, bracelet, schoolbags,etc. Good perfume/deodorant. This will make you look outstanding. Ask your friends which haircut & hairstyle looks decent on you. Just don't mesmerize as some boys may not like it. You will definitely realize which boy is interested in you.
just be yourself and confident. take care of your hair, and put some perfume on it after you wash it.
then feel sexy, because all these come from the inside. it is something you transmit to people when you feel sexy, have an open smiley face, and look straight to people. they will know you have nothing to hide.
the most important thing as I said is to feel well in your skin, so do something that makes you feel better and more beautiful.
I am doing all these, and I'm not artificial and I must say, even when I am dressed as a sporty, I turn heads.
so...just be yourself and magical things will happen you'll see :)
guys started noticing me more when I started wearing tighter sexier clothes. you can try to look sexier but not trashy or like a hooker, lol.like some skinny tight jeans with a nice sexy top. or a long tight skirt to your knees with a tight top. it doesn't matter if they think your slutty at 1st cause if you don't act like a slut then they won't see you as one. and once they start talking to you and getting to know you more they will start to fall in love with what's in the inside not outside.