We use tags in spoken English but not in formal written English.

They are not really questions but are a way of asking the other person to make a comment and so keep the conversation open.

Making a tag is very mechanical. To make a tag, use the first auxiliary. If there is no auxiliary, use do, does or did. With a positive sentence, make a negative tag and with a negative sentence, make a positive tag.

It’s beautiful, isn’t it?
He has been, hasn’t he?
You can, can’t you?
It must be, mustn’t it?
You know him, don’t you?
He finished it, didn’t he?
He will come, won’t he?

It isn’t very good, is it?
It hasn’t rained, has it?
It can’t be, can it?
Jenny doesn’t know James, does she?
They didn’t leave, did they?
He won’t do it, will he?

Notice these:

There isn’t an ATM here, is there?
Let’s have a cup of coffee, shall we?

To reply, use the same auxiliary:

It’s beautiful, isn’t it? ~ Yes, it is. I think it’s fabulous.
It isn’t very good, is it? ~ No, it isn’t. In fact, it’s terrible.

Although, the rules are very simple and mechanical, in order to use them easily in conversation, they have to be automatic. So you need to hear and practice them very often.