The following signs are signs of true love, not signs that he's got a crush for you (because he may be somewhat 'into' you but he may not love you at all!). If you are interested if he's just attracted to you, then read this page. But if you are here to understand if he truly loves you, there are the surest signs:
1 - He is interested in you, your thoughts, you ideas, your dreams, your goals, your jokes. He shows real interest, he remembers what you said in the past; he'll think about what you said and this is obvious when you 2 are together in various ways. More on this further on.
2 - He supports your interests, you goals. He respects them. This does not mean he shares the same interests as you, not at all, but he respects them therefore he allows you to pursue them and indeed supports them. This is very important, because you may engage in a relationship where you are doing all the supporting, where you are the one sharing HIS interests, but it's not the other way round. This will lead to a painful relationship for you in the end, and you definitely do not want that.
3 - A healthy relationship is about 2 people working as a team, it's about both of you. So, if it's all about him he clearly does not love you (he is selfish and incapable of true love). Equally, though, if it's ALL about you (if he becomes obsessed with you) that's not love either, but only an obsession.
You can read read the full list of signs with full explanation on THIS PAGE.
If he is not truly in love with you and you are crazy about him, there are ways to help him fall in love with you, as described on THIS PAGE.
But what if he does not love you? What if you two have been dating for a while, you seem to hit it off, yet he does not seem to truly fall in love with you? Do not despair: there are clever psychological tricks (all benign and in fact real fun for both of you) that you can adopt to help him fall in love with you; they are explained on this page.