[clivehawkins]

Don't tell your students what they are doing.
Give your students the list of questions.
They choose a partner and ask all the questions to the same person. They MUST NOT write the answers.

After you have presented your lesson on question tags, they then find their original partner and use these tags to see if they have remembered the answers they were told at the start of the lesson.

eg

You were born in July 1976, weren't you?

It's important that they don't know that they have to remember the answers from the initial question phase - this makes the question tag more authentic.
Remember rising intonation when there is some doubt. Level intonation when they are sure.

Enjoy!