Do not ask for special treatment by making the ordinary treatment harder for everyone behind you.

Exceptions have to be paid for by somebody. The extra minute at the counter, the rule bent, the arrangement made just for you: the cost lands on the queue, on the staff member managing it, and on whoever comes next with a genuinely unusual situation. From inside the request it looks like a small favour, because the people paying are behind you and out of sight.

Before you ask for something outside the normal process, look at who absorbs it. Ask when it is quiet, accept a no gracefully, and save the request for the times you genuinely need it.