I don’t have time to go to “High Quality Good Fair”. I wish I (went) there.
(Here, we use the past tense to express a wish about a present situation that is not true.)

The weather is very hot. I wish it (were) cooler.
(We use "were" for hypothetical situations in the present, especially with "I wish.")

We seldom write to her. I wish we (wrote) to her more often.
(This expresses a wish about a habitual action in the present that isn't happening.)

John doesn’t know how to swim. He wishes he (could) swim.
("Could" is used to express a wish about an ability or a past situation.)

John doesn’t buy the book. She wishes she (had bought) it.
(This is a wish about a past action that did not happen.)

We must communicate with you by means of e-mail or chatting, mustn’t we?
(The question tag matches the auxiliary verb "must".)

Nobody liked the play, did they?
(After "nobody," we use the negative tag question with "did.")

She’d saved money if she bought fresh food, hadn’t she?
(The tag question matches the past perfect "had saved" in the condition.)

The area was evacuated at once, wasn’t it?
(The question tag matches the past passive verb "was.")

She’s very funny. She’s got a great sense of humor, hasn’t she?
(The subject is "she," and we use "hasn't she" to agree with it.)

It never works very well, does it?
(The tag question after a negative sentence uses the positive form "does it.")

Mr. Smith usually remembered his wife’s birthdays, didn't he?
(The statement is in the past simple, so the tag uses "didn't he.")