I can't vote some of your answers here but I will say that I definitely agree to your answers. One key rule here is a basic in human relationship really. If learned this before I could have made a lot of friends. Thanks to the book of Dale Carnegie back in the old years: "How to Win Friends and Influence People". If someone says that a person is bad and all that, never look it that way. Always believe that there are good and greatness in other people regardless of how other people see them. Instead, just be nice, generous, humble and calm, respectful and polite. Learn how to appreciate people but be "GENUINE" on your lavish approbation. Don't hit his ego but know what he wanted, know his interest, be interested on what interest him. People love to talk about themselves, if he wants the top, relieve your pedestal and give it to him. It makes you less hostile and inviting. It makes you a nice person. We can't change people but we can be damn sure influence them and at the same time provide a harmonious relationship to one another. It is really hard to be interested with other people, but believe me, I still believe on what Dale called 'magic'. And that's the only magic I believe. Now I always feel better because meeting people is not always about me, not about presenting myself to them, but instead making themselves present to me.
So learn something about him, profile him if you could, know what he likes. Then when you meet him, say something like: "Oh so you are [name], I heard a lot from you [even though you heard bad things about the guy], you are the guy who wrote the system about [blah blah]. It is really awesome. I would really love to hear about your involvement on that project." Something like that, well you have your personality, you can say it better than me. If he is really difficult, maintain your composure and be always nice.