How do you ACTUALLY tell a guy you like him?

I've revisited this question many times, I do have someone special in mind at the moment, I do have a crush on him, although it's been quite a while and I've managed to get over most of the butterflies, but out of curiosity, if I knew him quite well and if we were friends/if I had a chance, how could I explain my feelings for him (must be spontaneous, because I don't know him that well and I just want to get it off my chest, it's a great burden).