Correct use of some words

YET and ALREADY

- We use YET only in negative and questions.
Mike hasn´t called YET.
Has Mike called YET?

- We use ALREADY in afirmatibe statement and questions.
They have ALREADY left.
Have they ALREADY left?

WOULD RATHER

- WOULD RATHER means "to prefer".It is followed by the simple form of the verb.
I WOULD RATHER watch TV than go to a movie.
He WOULD RATHER walk than take a taxi.

- In everyday conversation, we usually contract WOULD RATHER.
I´D RATHER watch tv than go to a movie.
He´D RATHER walk than take a taxi.

SUPPOSED TO

- we use SUPPOSED TO to express obligation or expectation.We can use it in the present and past tenses.
Lucy is SUPPOSED TO be here.
They WERE SUPPOSED TO arrive last night.

USED TO

- USED TO.Describes an action that was done for some time(as a habit, for example) in the past but that does not happen at the present time.
I USED TO smoke.
(Now I don´t smoke anymore)

He USED TO study French.
(Now He doesn´t study French anymore)