When have I to use "don't + pronoun"/"doesn't + pronoun"? I saw it a few times and I'm not sure how to use it.
An example could be:
You're going to school, don't you?
In all the varieties of English that I am familiar with, a tag question on a sentence with an auxiliary (or a form of be even when it is a full verb) uses the auxiliary in the tag question, not do:
You are coming, aren't you?
He will win, won't he?
I can finish it, can't I?
He is, isn't he?
Only when there is no auxiliary, do we use a form of do:
You like it, don't you?
I have heard some English speakers (from Pakistan, I think, but I'm not sure) using isn't it as an invariable tag question. I don't know of any who use don't you/we/they and doesn't he/she even where there is an auxiliary, but I would not be terribly surprised if there were a variety of English somewhere that did do this.
Don't is a contraction of "do not". Doesn't is a contraction of "does not". Do and Does are forms of the verb to do. Which one to use just comes down to conjugation:
I do. You do. He does. She does. We do. They do.
You like apples, don't you?
He likes cake, doesn't he?
The two acceptable forms of this sentence are,
"You're (You are) going to school, aren't you?" (are you not?)
"You go (You do go) to school, don't you?" (do you not?)
If you look at the sentences above you will see that they use the same auxiliary verb in the question as they do in the main sentence. So in the first sentence we see can and can't; in the second we see will and won't; in the third we see have and haven't; in the last wee see are and aren't. Notice that we can't use the main verb dance in the tag. We have to use an auxiliary verb.
Now look at the sentence below. Which auxiliary can you use here:
In sentence (5) we have a problem because there is no auxiliary verb in the main sentence. When we don't have an auxiliary verb in the main sentence we have to use a dummy auxiliary. The dummy auxiliary in English is the verb DO. When we don't have an auxiliary but we need one, we always use DO. It is like a spare tyre that we keep in the back of the car:
Don't you can also appear in negative imperatives:
Don't you open that door!
Don't you touch that stove!
Normally, imperatives in English don't require any subject (addressee) pronoun. The "you" is acting as an intensifier in these sentences. Whoever is giving orders is angry, or will tolerate no disobedience. It is similar to the effect of placing a swearword in the same position:
Don't [bleep]ing open that door!
or appending the addressee's full name:
Don't open that door, Jane Windslor Wexler!
The tag question is opposite to the answer you want to suggest. So if you believe that someone goes to school and you want them to confirm it, you might say:
You go to school, don't you?
but if you think (or suspect) they don't go to school and you want them to confirm that, you could say:
You don't go to school, do you?