Should vs would vs ought vs must
I don't get it at all when I have to use each one of those words. 
3 Answers
I'm assuming you mean in English...
You should clean your room. This means that it would be nice if you cleaned your room, but it isn't absolutely necessary. Before you go to bed, you should clean your room.
You ought to clean your room. This is very close to the one above, but is not used as often. Maybe even a suggestion. Hey, before we go to dinner, you ought to clean your room.
You must clean your room. This is a necessity. In order to get your allowance, you MUST clean your room.
Would - Like I put above... Before we go to dinner, it would be nice if you cleaned your room.
Would / Should / Ought to / must son modals, por lo que le sigue un infinitivo sin to y las oraciones interrogativas y negativas se construyen sin el auxiliar do.
Would you do it if I paid you? ¿Lo harías si te pagara?
You should not drink and drive. No deberías conducir si has bebido.
You ought to do it. Deberías hacerlo.
She ought to go out more often. Debería salir más a menudo.
I must leave early. Debo salir temprano.
Cuando necesitamos otras formas utilizamos "to have to" = tener que:
He’ll have to come tomorrow. Tendrá que venir mañana.
The other modals are:
can / could
will / (would)
shall / (should)
used to / (ought to)
may / might
Otra cosa que quiero agregar: "Would" está usado para formar el condicional. Por ejemplo: Te ayudaría pero tengo que irme.=I would help you but I have to go.
