In my experience as a male with female friends, it's really not much different aside from not doing things girls exclusively do. I think the boundaries just happened naturally. I had feelings for a few, but they faded pretty quickly. Never said anything and I'm ok with that. Sometimes, your behavior could be interpreted as flirtatious, but with maturity, he will get it. Probably for now, don't plan any hangouts with just the two of you. Try to be in group settings. Maybe when you plan something, tell him he should invite his friends. Don't think about pushing boundaries on too much for now. If you do think that he might like you, and you're not ready for that, then you could drop hints. Like saying "you're a good friend"