When someone asks you, "How are you doing?" in a casual social setting or as a polite greeting, they typically expect a brief and positive response. In most cases, a simple "I'm doing well" or "I'm doing good" is considered an appropriate and sufficient reply.
In these situations, the question is often more of a social nicety rather than a genuine inquiry into your well-being. It's a way for people to acknowledge your presence and engage in a friendly exchange without delving into personal details. Similarly, when you respond with a positive answer, it helps maintain the flow of the conversation in a positive and light-hearted manner.
That said, some people might genuinely be interested in knowing more about how you're doing, especially if they are close friends, family members, or if the context of the conversation suggests a deeper interest in your well-being. In such cases, you can choose to share more about how you're feeling or what's happening in your life.
In general, reading the context and the person's body language and tone can help you gauge whether they are asking out of politeness or if they are genuinely interested in a more meaningful conversation. If you feel comfortable sharing more, you can do so, but if not, a simple and positive response is perfectly acceptable in most social situations.