Is this one of those hypothetical things where it’s actually happening but you’re asking on behalf of someone else? Perhaps I can write down some pointers if it might help you… or for whoever out there that might want to confess to me:
1. Please just be genuine. I really don’t care how you do it (although unique methods would probably score more memory points), but I would really appreciate for you to just be very sincere with how you do it.
2. If it helps, I write letters… so I would really appreciate if there’s wording in how you confess (but please don’t ask someone to ghostwrite it for you, though. Once again, refer to point one).
3. If this guy is seriously a friend, I hope he’s interacted with me several times before. I’d appreciate it better if he… didn’t come from out of the blue. It’d be easier for me to fathom the confession that way, to be honest.

And some things to consider, I suppose.
1. Make sure to time it right.
2. I don’t normally seriously date for leisure (or at least I don’t think I can), so perhaps you can change that?
3. No confession is fool-proof, I wouldn’t want to lie about my feelings too if I don’t happen to see it develop in your favor.

I hope this is enough?