Not a teacher.
Since I joined this forum, I've become far more cautious using 'always' and 'never'. 'As a rule' has proved to be a much safer phrase
You might find the examples below useful.
Let's go to the cinema, shall we?
I'll hold that for you, shall I?
Hand me the knife, will you please?
This is the final match of the season, is it? ~ Yes, that's right.
So you can run a mile in four minutes, can you?
So you're getting married, are you? How nice!
You can make a positive statement (to make a guess, expess interest, surprise or concern) and then add a non-negative tag to ask if the assumption is correct (same-way tags).