haha... man oh man. don't be a loser and hug girls at school like all those freshman kids who think its cool hugging one girl after another.
girls go around hugging other girls. ... i never thought "wow that guy hugs girls... he's so cool."
no, usually i look at their nervous facial expression as they hug a girl and after they pull back after... they look so nervous its pathetic.
---
when you're completely into a girl and totally comfortable around her... it doesn't matter HOW you hug a girl. it'll just be totally natural.
and naturally if her arms are going over your shoulders around your neck, you'll NATURALLY go around her waist. if you naturally go over her shoulder, she'll NATURALLY go around your waist. it doesn't make a difference. its subconscious... you won't even think of it.
don't be juvenile and compare kisses to hugs, and how hugs lead to kissing, which leads to touching in the dirty places. meaningful hugs feel just as good as a REAL kiss.
---
i didn't give you an answer on how to... but why it's just dumb.
it comes naturally.
also... grab their ass after a few seconds for fun as as a "joke". they love getting touched if you're not an ugly creep.