Switching from the Formal to Familiar “you”
Spanish has 2 different pronouns for you — tú and usted.
You can use only informal you (tú) if you ask one of these question:
¿Puedo tutearle?
¿Puedo llamarle de tú?
If they answer yes, you don´t need to use "usted".
Sometimes, people do not want you to use usted to address them. These are some of the phrases you might hear them say:
No me trates de usted. (Don't treat me as an "usted".)
Dime de tú. (Call me "tú".)
Trátame de tú. (Treat me as a "tú".)
Por favor, tutéame. (Please, use tú. — Non-literal translation)
Puedes tutearme. (You can use tú. — Non-literal translation)
Puedes hablarme de tú. (You can talk to me as a "tú".)