The question is: how much do you know about him? If you know what he likes, and are into any of it, start talking about how you feel about those things, and don't be worried about disagreeing. If you don't know, just ask him the things he's really into, then start talking to him about anything you know - be it asking to acquire more knowledge, or just opinions and/or feelings. Talk about funny things that happened during your day, and be open to listening to things he has to say - including about things that are worrying/bothering him, if any. But let those come out on their own.
Try to talk about things that are gender neutral or something he'd probably be more exposed to, but you can also fill him in on details of things that only you or your friends get (or try to, haha) to make him feel a little included. But remember, don't get lost in your own thoughts on these things as to dominate the conversation - share the chat, and make him feel interesting and included, like the things he says matter to you.
Be friendly, be thoughtful, be interested, and most importantly, be yourself.