The standard reference for this is "How to Win Friends and Influence People" by Dale Carnegie. I have not read it myself.
Much of it boils down to gothgirl420666's advice, except with more technical help on how. (I think the book is well worth reading, but it basically outlines "these are places where you can expend effort to make other people happier.")
One of the tips from Carnegie that gothgirl420666 doesn't mention is using people names.
Learn them and use them a lot in coversation. Great them with their name.
Say thing like: "I agree with you, John." or "There I disagree with you, John."
r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.