Somebody please tell me how to hug a boy?!

I'm a really awkward girl and these things don't come naturally to me at all. How do you know when it's appropriate to hug a boy? I am sort of friends with this boy at school, but I am really reserved and exceptionally hopeless at making any form of physical contact. I really like this boy, and I want to give him a hug! Just because I have all this emotion in me, all bottled up, but I'm so restrained as a person that I can't let it out or show him how I feel. So I want to give him a FRIENDLY hug. But how? I'm 5ft tall and I think this complicates matters. First of all, do I extend my arms outwards kind of slowly to indicate that I want to hug, or do I just grab him? Secondly, where do I put my arms and my face? I'm guessing the arms will go around his middle (the neck wouldn't really be for a casual hug, would it? Idk), but what about my face? Put it over his shoulder next to his face, or bend my head and put the side of my face against his chest? As I'm short, I don't think my head will reach his shoulder! But I don't want to feel like a child with my head on his chest, and that might be too much physical contact? And when? I'm thinking, next Thursday when the results come out, if he did well I could jump in with a congratulatory hug, to make it seem as casual as possible ... but IDK! When do friends hug each other? God, just read this back and I sound like a total troll, but I'm honestly not and I'm clueless about all these social norms. With him being a boy and me a girl, how do I do this without being awkward or making him think I fancy him? Reps to anyone with good advice! Please just tell me how to hug him ... :o

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