How could i forget about someone who only treat you as a friend?

You're not going to be able to just forget this person. If you're still in school just know that soon enough you'll both go and do your own thing and he won't be on your mind so much. But this is a part of your life and is shaping the person you're becoming so just go ahead and live it. I know it sucks to hear that from someone who makes it sound so simple when your heart very likely aches for this person, but it really is just a one day at a time kind of thing and one day you'll notice he doesn't quite pull on your heartstrings so much.
Then again, I'm giving this advice under the presumption that you have told him or at least given obvious hints about your feelings and he is still keeping it platonic. If not, go talk to him!

Buy a book about anger management.

You have to seize and desist all contact. And I mean ALL CONTACT. Nothing. Nada. As long as the person is in your life - even remotely (i.e. via mutual friends and you run into him when you guys all hang out etc) - you will have a very hard time getting over them. The importance of no contact is that it allows you to heal and be by and for yourself. Staying in touch with someone like that is sort of like salt in the wound. Every time you see them, it is like you added more salt: the wound never heals. Another reason for no contact is you cannot stalk them, find out about their life or if they are dating someone new etc etc. That is important because you will never be able to move on if you keep being informed about him and whereabouts. You have to realize that love is a two way street. You cannot make anyone love you or care about you. So, take whatever dignity you have and MOVE ON. Cutting out that person out of your life in every way possible is an important first step. Trying to be friends is stupid because you know you love him, you cant be buddies with someone you love.

Bottom line: stay away. Dont look at him, dont cyber stalk him, dont ask about him through friends. I went through a similar thing and it was painful and I promise you, if you dont stay away, you will drag out the pain and inevitable longer and longer. Staying around people who dont love you just makes you older and ugly.

I wanted to do that but it isn't the right time as we are having an important exam in 3 months time.
Whenever he is with a girl(my so called best friend), that girl act so sluty and it broke my heart to see him sitting beside her laughing.

get rid of the dude

You're grammar is terrible.

Obviously your choices are vague. I don't suggest neither of the above. You are simply wanting to fix this problem with some form of stress and/or retaliation. I suggest you simply keep taking him as a friend as is. You won't change anything by simply asking everyone else because obviously its just the internet and random BS comes up. I took the same approach and you should be able to do it as well. Takes time until you realize you don't actually put much of attention to the affection anymore.

well, I'm in the same kind of situation...I really don't know what to do. It's seems quite obvious that I'm into him, but I don't know if he is into me. It's like one of those hate/love thing. What should I do? Besides ignoring him...

Cut them out of your life. Its the best and only way you can move past your feelings. Come on people we all know this is the best option. Just because its not fair to them doesnt mean its not the right thing to do. You wanna know why? bc in the end its you that matters. People always let you down so why put other peoples feelings before yours. You should be focused on your happiness. Yes that sounds selfish but were all selfish just not all the time.

Unwanted love, boo hoo. Welcome to the club. I've ignored so many in my life and I have no regrets over it now. Plenty fish in the sea...

TRICK them into selling me thier SOULESS

You really don't give many options. I've had this same sort of thing happen [switch the gender's though]. She was my best friend for months and i had a huge crush on her, and she found out so it got kind of awkward, but eventually we both realized it didn't change how good friends we are and we still talk quite often when we see eachother. there's no point hating someone just because they don't feel the same way about you, and ignoring them isn't a good idea either.

I just have to say, those are all terrible options. If you had a good friendship with this person prior to you having feelings for them, I don't think you should cut them out of your life. You could try distancing yourself from them slightly, that way you have some time to reflect on your feelings and gradually move past them. I think the best thing to do is just give it time :) Good luck!

Well I think it's a great exercise for you to learn how to control your heart.
Keep reminding yourself that exams and your future are much more important than someone who DOES NOT love you.