Nota Cultural: usted/tú
Tú and usted both mean "you," but are used in different situations.
Tú: Is used informally, among friends and family members. It is also used among younger people, whether they know each other or not. You may use tú with a colleague who is your own age and/or rank. You should always use tú with children. there are, however, cultural differences between countries. For example, South Americans generally use a more formal speech than Spaniards.
Look at the following conversation between a sister and brother. They address each other as tú.
Jaime: ¿Ya estás lista para continuar?
Jaime: Are you ready to go yet?
María: En un minuto. ¿Tú quieres ir a casa ya?
María: In a minute. You want to go home now?
Jaime: Sí, estoy cansado.
Jaime: Yes, I'm tired.
Usted: Is used in formal situations. It is used as a sign of respect for an older person, or in most professional settings. In the case of older people, they may follow your lead, or they may use tú. In a professional situation, usted should be reciprocal.
Look at the following conversation. Notice that when the colleagues are speaking together, they use tú, but when Victor calls their boss, he uses usted as a sign of respect.
Ramón: Tú debes llamar a la jefa para pregunarle cuándo necesita los papeles.
Ramón: You should call the boss and ask her when she needs the papers.
Victor: Buenos días, Sra. Menéndez. ¿Cómo está usted? ...Estoy aquí con Ramón y Sandra, y queremos saber cuándo usted necesita los papeles...Gracias...Sí...Buenas tardes.
Victor: Good morning, Mrs. Menédez. How are you? ...I'm here with Ramón and Sandra, and we would like to know when you need the papers...Thank-you...Yes...Have a good afternoon.
*** In a real-life situation if you are not sure which to use, the best thing to do is to wait for the other person to take the lead.