When we have an obligation to do something or we remind others of their obligations we usually use the verb deber (must) and tener que (to have to), we can also suggest debería (should, ought to) or we just request it podría (would or could). Let's see the different forms.

obligation

Tú debes estar en clase cuando suene la campana.
You must be in the classroom when the bell rings.

Debemos contener el fuego.
We must contain the fire.

Tenéis que cenar en mi casa sin falta.
You guys have to have dinner at my house with no excuses.

Tú y yo tenemos que firmar los contratos primero.
You and I have to sign the contracts first.

suggest or advise

Lo deberías imprimir.
You should print it.

No deberíamos cometer los mismos errores que nuestros antepasados.
We should not make the same mistakes as our ancestors.

¿Por qué debería yo contratarlo?
Why should I hire him?

request

¿Podrías venir el martes que viene?
Would you come next Tuesday?

¿Podrían despertarme a las 7 de la mañana?
Would you wake me up at 7am?