Some of Hemingway’s best writing advice is featured over at BrainPickings. Here’s one tidbit that comes with a prompt built in:

Listen now. When people talk listen completely. Don’t be thinking what you’re going to say. Most people never listen. Nor do they observe. You should be able to go into a room and when you come out know everything that you saw there and not only that. If that room gave you any feeling you should know exactly what it was that gave you that feeling. Try that for practice. When you’re in town stand outside the theatre and see how the people differ in the way they get out of taxis or motor cars. There are a thousand ways to practice. And always think of other people.

~ Ernest Hemingway, On Writing

Give it a go. Walk into any room and see if a feeling comes over you. Name it. What’s the emotion? Isolate it. Where is it coming from? Listen to people talking. What are they saying? What are they not saying? What are their bodies saying that their lips are trying to conceal? Describe the room. What’s the mood? Jot it all down. Practice another time. Another room. Another feeling.