You should say:

　　Where and when you met him/her

　　What you do together

　　Something about his/her appearance and personality

　　Explain why you think you are such good friends

　　I met my best friend while I was at university. He was in the same class. At first, he scolded me for leaning back on my chair but, after a while, we began to become good friends. I used to meet him regularly at an Internet café. He went there regularly. We would spend hours there together. He would always lend a hand to me because I didn’t know much about computers at that time.

　　He’s a humble guy, never shows off his knowledge, even though he can. He’s sincere and doesn’t mind mildly scolding you or even himself in all the same sentence. . He is usually very sociable, but sometimes he can also be a bit shy. He is good at soccer and volleyball and used to be on the school team. He’s quite muscular and his hair is frizzy. He has very droopy eyes, like a puppy and a very wide mouth.

　　I think the main reason we are such good friends is because we have a lot in common and we both have the same kind of humour. We also always support each other whenever we need help. I think we are such good friends because we don’t feel we ever have to pretend around each other, and we are really helpful to one another. I will miss this guy a lot if I go overseas but since he is always at the internet café, I can email him, and he’s probably right there to receive it!