I like this idea! I feel like the current questions are insufficiently "stupid," so here's one: how do you talk to strangers?
One of the most simple lessons that I got a lot of milage out of is: don't be afraid to state the obvious. A lot of conversations and human interactions are more about the positive vibe that's being created than about the content. (Somewhat less so in these circles.)
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.