answer:(1 & 2)State it quickly, clearly, and directly. Especially if you do actually enjoy the guy’s conversation—just say “I’m really enjoying talking to you, but I think you should know I’m not looking for anything tonight. I’m just having a nice evening.”, and give him the opportunity to save face and wish you a good evening or shift gears and keep chatting with you. Most guys, I think, will appreciate your candor, but you have to be prepared for him to stop talking to you (even if you’re very sweet about it, it’s still a little embarrassing to be rejected). (3) Yes, we always want to know the reason, but don’t offer it unless we ask. (which will be almost never)