Social Encounters
You also need to decide the objective or consequences of the social encounter—what the PCs can achieve and what happens if they fail—and the form of the challenge. It might be an online debate, a private meeting with a powerful person, or some kind of contest. Just like with combat encounters, think about the environment, with a particular eye toward the other people around. Is there a moderator the PCs can sway? Are they in an expensive private room in the hottest nightclub or at a crowded coffee shop? Is the atmosphere oppressive? Hopeful?
You might find the PCs' goals end up being quite different from what you initially thought they would be. Fortunately, social encounters are adaptable. Thinking of their likely objective helps you construct the scene in your mind more easily but shouldn't limit you.