ya-sabes

You can use ya sabes when you know that your listener shares your understanding of a situation. It is especially useful for shared misery.

To force someone to spell things out, you could answer Ya sabes with ¿Ya sé qué? (said with falling intonation) What exactly is it that I know what, according to you?

¿Sabes?

The tag ¿Sabes? works for You know that, right? For example: Siempre voy a estar contigo, ¿sabes? We'll always be together, you know that, don't you?

Standing alone, ¿Sabes? is also a shorter and more informal version of ¿Sabes qué? It is useful for bringing up something you just remembered. ¿Sabes? Olvidé tu número de teléfono. You know what? I forget your number. Could you tell it to me again?

¿Sabes qué?

Besides meaning Guess what?, ¿Sabes qué? can preface an angry retort: ¿Sabes qué? Ahórrate tus explicaciones. You know what? Just save your breath.