How you can identity an emo kid:
Black, thick framed glasses
An extra small t-shirt/cardigan
Pretty tight pants
Converse All Star shoes/hightops
Possibly a studded belt
Usually carrying around some notebook/poetry book/messenger bag
First of all, emo = emotional.
Your typical emo kid is usually sad, upset, maybe angry and the world. They always talk about heartbreak. Always about misfortunes, and never see the upside to things. In short, emo kids are emotional.
That kid who sits under the tree writing poems about the girlfriend he lost in grade 4.