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."
This is a piece of advice that most people disagree with, and so I am reluctant to endorse it. Knowing people's names is important, and it's useful to use them when appropriate, but inserting them into conversations where they do not belong is a known influence technique that will make other people cautious.
(While we're on the subject of recommendations I disagree with, Carnegie recommends recording people's birthdays, and sending them a note or a call. This used to be a lot more impressive before systems to automatically do that existed, and in an age of Facebook I don't think it's worth putting effort into. Those are the only two from the book that I remember thinking were unwise.)
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.