In my opinion, if you really like someone then you should tell them exactly how you feel. However, you have to ensure that they are not engaged with someone else and that they are also interested in knowing you. Therefore, take your time before saying anything to them and instead try building a friendship bond.
I concur with LoiseMatch save one thing. Listen to your heart and pay very close to social ques and norms! always avoid awkwardness when it comes to love confessions! So when you give it time, you're really just waiting for positive ques indicating his interest and then the proper time to confess! Often I find waiting for both of those and being sure that the moment is a good kiss moment makes for some awesome memories! ;oD
I also like a guy, and I will tell him tomorrow after class. Anyways, if you like that boy, tell him how you feel on him and why. That guy you like will tell you how he feels about you afterwards. If not, there are many more fish in the sea. -New User
Before baring your soul and risk the injury of rejection, it might be prudent to approach them in a casual but friendly manner and ask them to join you at a social function of some sort. This would give you the opportunity to know them a bit better and give you a better framework to express yourself to them.
I wouldn't tell this person you are in love with them, start by telling this person you think their cool and would like to hang out with them one on one. Keep it casual at first, If they accept then after dating you will get to know the person better and you will find out if you truly do love them.