Erm, a way that you could go about telling him could be summat like erm..
'can i tell you something serious without you laughing at me?'
*He replies*
'Well, i don't know how to say this, it seem's hard for me *little giggle* but erm.. What would you say if i told you that i liked you? i mean like as in more than a friend?'
Dunno if that helps but it's what i said to my now gf when we were just friends :) hope i've helped you :D