I wouldn't express my feelings for a while till you get to know him better but the best way is to strike up a conversation with him about something you both like or something he likes. The more you just talk with him the better and in time you can actually tell him how you feel about him. Start off slow and work up to it . Take your time.
Depends how old you are. "Friendship" can easily be offered by simple polite conversation, and possibly an invite to do something together., an acitivity of some sort.
A child can make friends without actually expressing how they feel and just by acceptance in play. It's simple and innocent. It really does't have to be more complicated than that. You don't need to walk up to someone and say the words 'Will you be my friend' .. It's a lot more subtle than that. Casual freinds are easily made.
However .. taking it into a romantic 'realm' is a lot more complicated than that. Create a casual friendship first .. get to know each other .. THEN, if it feels right let your friendship develop into something deeper.