taken from wikiHow

How to Know if a Guy doesnt like you back?

Steps :

1. 1
   Watch body language. Body language says a lot about a person, if he rarely ever looks at you, or isn't smiling (and has a vacant expression) while looking at you, odds are, he isn't into you. If he's interested, usually he will be looking at you a lot, and he will be willing to start small talk. Watch his feet while talking to him. If they are pointing towards your direction he's interested
2. 2
   Pay attention to if he's ignoring you. If he ignores you during the day, and he shows hardly any interest, and looks at you once, then it's quite obvious he doesn't really find you interesting.
3. 3
   If he's talking to other girls, and not to you, it's just quite obvious that he's probably interested in one of them. It also may be a possibility he's trying to make you jealous, if your not sure, look at him, and if he's talking to the girls and glancing at you, that could be one of the signs he likes you and is trying to make you jealous.
4. 4
   When he's looking at you, look at his eyes; if his pupils get larger, then he likes you. This has been proven that if a human really likes something, their pupils will enlarge.
5. 5
   Drop something, anything, a book, a pencil, possibly right in front of him, if he is willing to help you, there is a good chance he likes you, especially if he starts conversation with you right after. Guys usually always help out girls they like. Don't confuse liking with kindness.
6. 6
   If a guy is acting rude to you, making fun of you, or talking meanly and laughing about you with his friends, it's not a good thing. Odds are if he's treating you like this, you're onlyreally liking him because of how attractive he may be. So at the point, it would definitely be the time to move on.
7. 7
   If you find out he doesn't like you, don't be mean. Be polite and Move on.

Tips:

• Sometimes, if he doesn't like you, it definitely can be a hard thing, especially if he's on your mind a lot. But don't lose hope! Just because HE doesn't like you, doesn't mean another wonderful guy won't. If you've ever heard the saying, "There are other fish in the sea.", it's true!
• Be aware! Sometimes a woman's instinct is correct right from the start! He could actually like you! If he likes you be aware of the signs.
• Dealing with rejection is hard, but, remember, crushes will come and fade with time. The most important thing is that you have friends and family that will stick by you. Talking with trustful friends and family and you will get through it.
• Accepting and coming to terms with what is going on and what has happened is one of the hardest things to do, but you will move on. And you will accept it and come to terms with it.
• Initiate a friendship with him. Starting a friendship is easy, and usually starts out with just a sentence. Start on topics such as the weather, school, work, anything really. This actually is the best way to getting what you want, because you figure out more about him, and who he is. You could actually discover you don't like him as much as you thought you did. If friendship is just making you like him more, than move a little bit forward. Be a bit flirty with your friendship. But beware, he could be just interested in the friendship you share.
• In the end, if you can't tell you can just ask him if he does or doesn't like you. Honesty is the best policy.
• When your confused if a guy likes you back he probably doesn't but if you know he likes you then he likes you.
• Even though every guy behaves a different way no matter what personality or flaws he holds they all make an effort to get to you. If he likes you he will text, call, talk to etc. He might be shy, cocky, insecure but if he's truly interested he'll get to you. If you find yourself doing all the work there's something wrong there.

• If he is telling others that he wishes to kill himself or never see you again because he knows that you like him then i think its pretty obvious that he doesnt like you

Warning:

• He's always hands off if he is dating someone. Remember, how would you like it if some girl was trying to get your man?
• Remember your limits, and his.
• He could have a possible interest in you if he has a girlfriend and he secretly is keeping his crush on you to himself by telling his girlfriend things such as "She's Weird" or "Ew, she's ugly" but this always could be true, so watch for close tall tail signs that he's interested or not, and get more information by watching his actions towards you.
• The information in this article is heavily stereotyped. All guys are different, just as all girls are different. As such, these are just tips that may or may not be true.
• Boys are like buses if you miss the first one the next one will be arriving soon.
• Don't be too all over him odds are you'll look needy or desperate and that is a turn off.
• We chase the people who ignore us and ignore the people who adore us. Live by that motto a lot of guys will be coming your way.
• Don't play hard to get or hang around other guys in front of his company not only is it obvious what your doing but you might get an unwanted label.