After you have blindfolded somebody and are spinning them around, ensure that they are not trying to keep track of where they are. Ask questions like, what’s the capital of England?, or even better a times table question while spinning them, so they can’t have their mind on the job of trying to figure out which direction they are facing.
After spinning and asking them questions, ask them, “How many times have i spun you and where are you facing?” Regardless of the answer, don’t let them know if they are correct or not.
You could also make a game of it as in ask them times tables question and the sooner they question one correctly you stop spinning so the less disorientated they will be.