Listen. If they say your idea sucks, listen to the feedback, take notes, and ask for contact info. Then go fix the problems, or come up with another idea and demonstrate you listened.
Get to the point. People like Ron Conway are busy. They are wildly rich, so the only thing that is limited in their life is time. You are taking away some of their most precious resource, so get to the freaking point. Don’t try to chit chat or ask about their kids or make small talk. Go right for the big ask. They are used to it.