1. He cancels plans
You initiate making plans, and he reluctantly agrees. An hour before you are to meet up he cancels and comes up with a bs excuse. If he does this once in a blue moon and the reason is legitimate then you have nothing to worry about, but if this is a common thing then don't kid yourself.
2. He takes forever to respond to your calls/texts
Sure he might be working or busy and isn't living on his phone. However, if you find him hanging out on social media posting away, meanwhile it has been 3 days since he replied to your instant message then maybe you should reconsider whether you should be devoting your time to him at all.
3. He doesn't give you attention
If you're trying your best to get his attention and find out about him, and he doesn't give you the time of day- he may not be into you. A man should chase to some degree, and if you find yourself literally stalking him to get him to talk to you, then he isn't the one for you.
4. He says he isn't ready for a relationship
Of course there are many legitimate reasons for why someone may not be ready for a relationship; work, school, recent break up, etc. If a guy likes you however then he wouldn't want to date other girls and would do whatever it takes to make you his and be loyal.
5. He talks to you about other girls
This is a big sign that either he is trying to make you jealous, or more than likely he isn't feeling you. If the guy you like is talking about how hot your roommate or sister is to your face, then they couldn't care less about your feelings, nor do they fancy you.