1) Wearing glasses
2) Don't like to mix with people, in other word, not very socialize person
3) Always with the book around them
4) Very tidy hair style
5) Always been bullied by other people
6) When they walk, they will look down and don't look around
7) Put button up until their neck

Nerd may look not very attractive, but they are very smart person. Most of the successful person in the world is the nerd. For example, Bill Gate. During his study, he always been bullied by his classmate because don't know how to socialize. But, look at him now. He is the richest person in the planet.
Some girls prefer to hang out with the coolest and handsome guy. Some may also like to hang out with the nerd especially during studying, because they always help you in study and they are so smart. Nerd can also sometimes look very charming..
p/s: do you like nerd guy? =)