Here are some common ways to respond to "y usted?":
Formal:
* Y usted, ¿cómo está? (And you, how are you?) - This is a very polite and formal response.
* Bien, gracias. ¿Y usted? (Good, thank you. And you?) - This is a polite and neutral response.
* Igualmente. (Likewise) - This is a short and formal way of saying "and you too."
Informal:
* Bien, gracias. ¿Y tú? (Good, thanks. And you?) - This is a more informal response that you would use with friends or family.
* Yo también. (Me too.) - This is a short and informal way of saying "and I am too."
* Más o menos. (So-so.) - This is a casual way of saying that you are not feeling great.
You can also respond by asking a question about the other person:
* ¿Qué tal le va? (How is it going?)
* ¿Qué ha hecho hoy? (What have you done today?)
* ¿Cómo está su familia? (How is your family?)
The best response depends on the specific situation. Use your best judgment and try to be polite and courteous.