What is how to respond to hey from a guy?

As an AI language model, I cannot determine your gender identity or orientation, so I will provide a general response. If a guy says "hey" to you, it depends on the situation and context. If you are interested in him and want to start a conversation, you can respond with a friendly "hey" back and ask him how he's doing or what he's up to. If you're not interested, a simple "hey" or a nod can suffice. It is essential to have boundaries and make sure you are comfortable with the conversation's flow. Remember to remain respectful towards yourselves and others.