Ever, Never, Already and Yet

We use 'Ever' ;

a. in questions.
Have you ever been to Scottland?
Has she ever met the President?

b. in negative questions
Haven't they ever been to America?
Haven't you ever eaten English food?

c. and in negative statements using the pattern nothing.......ever, nobody.......ever

Nobody has ever said that to me before.
Nothing like this has ever happened to them.

d. 'Ever' is also used with 'The first time....
It's the first time I've ever eaten snails.
This is the first time I've ever been to Scottland.

'Never' means at no time before now, and is the same as not ..... ever:
I have never visited Istanbul.

!!!Very important Tip!!!
You should not use never and not together:

I haven't never been to Italy. this is wrong !
I have never been to Italy.this is right

Position: 'Ever' and 'never' are always placed before the main verb (past participle).

Already and yet:

Already refers to an action that has happened at an unspecified time before now. It suggests that there is no need for repetition,
a. I've already drunk 3 coffees this morning. (offering another one to me!!!)
b. Don't write to Kevin, I've already done it.

It is also used in questions:
a. Have you already written to Sandra?
b. Has she finished her work already?

Position: already can be placed before the main verb (past participle) or at the end of the sentence:
a. I have already been to Toronto.
b. I have been to Japan already.

yet is used in negative statements and questions, to mean (not) in the period of time between before now and now, (not) up to and including the present.
a. Have you met Julie yet?
b. I haven't visited the London yet.
c. Has she arrived yet?
d. They haven't drinken yet.