unless you are using sleep masks make sure that the cloths you are using for the blindfold are thick and dark and can be folded or rolled up and is long enough to tie up securely, a good example would be a t shirt as you can fold it up and tie using the arms pieces, a tea towel is another good option, make sure the material over the eyes is not uncomfortable, and that most of the face is not covered. The less the blind man knows about the game before they are blindfolded the better, and total darkness is best, with no peeping as far as the blind man is not frightened. To disorientate the blind man spin them around ensuring that are confused about which direction they are facing. Make sure that you take it in turns so that you get to be the blind man too.
If your child has never been blindfolded before, explain what a blindfold is before blindfolding yourself, or blindfold an older family member, and give them a simple object and explain to your child that because the family member is blindfolded they can not see and have to use their hands in order to correctly identify the object without removing the blindfold. The blindfold the child while they are safe on your knee, explaining that there is nothing to be scared of, but if they do get scared you will remove the blindfold, and start simple by asking them to identify a simple object that they use every day like a soft toy.