emo is mostly vocals.
there are no solos, and if any, its probably 5-10 seconds.
emo tends to have simple catchy riffs that complement the vocals.
stylistic influences are usually umm.. bad relationships and bad parents. to be a good emo songwriter you have to have lived a life teenagers can relate to, but it must be an emotional one...
umm most emo songs complain about something, or are begging and pleading somebody to do something.
emo song lyrics usually have something to do with love

some examples of this.

So cut my wrists and black my eyes.
So I can fall asleep tonight or die.
Because you kill me.
You know you do, you kill me well.
You like it too, and I can tell.
You'll never stop until my final breath is gone.

if you are looking for influences... the emo bands that always come to my mind when i think of emo are fall out boy, hawthorne heights, ...death cab for cutie maybe?...