Emo boys like emo girls that are like emo boys that like emo boys to be like emo girls.
First and foremost you need to be your self, but if your looking for a little edge to impress him, this will help.
Break this two ways...
Mental: Talk with him about your favorite music,banda,and songs. Emo people love to talk about music.
Share some of your problems with his, he can help you and you will love helping him!
Not for the less important (but not to most boys :p)
Physical: in my experience your body type isn't that big of a deal, but it does help if your skinny.
Makeup is veryyyyy important, eyeliner is a must.
Makre your hair like the ultra cliche emo and he will love it, try something differnt like dying the bangs blonde.
Lastly remember this.....
Emo boys like emo girls that are like emo boys that like emo boys to be like emo girls.