Te or Le, Tu or Su?

The words for you and your follow the same choice as the verb:

• tú → te (to you) and tu / tus (your): Pablo, ¿te traigo algo?
• usted → le and su / sus: Señora, ¿le traigo la cuenta?
• ustedes → les and su / sus: Señores, ¿les traigo algo de beber?

Use tus or sus when the thing owned is plural: tus llaves, sus llaves. Tu (your) has no accent; tú with an accent means you. Su can also mean his, her or their, so the way the person is addressed (Señor…, Oye, Ana…, Niños…) shows that it means your here. In Spain a group of friends or children gets os and vuestro, vuestra, vuestros, vuestras (¿Os traigo agua?), which is also accepted.