My favorite is using random chance games for choosing reward or punishment. Either slips of paper in a bowl to choose from, spinning a wheel, rolling the dice, etc.
Dice are fun, because you can add additional variables. Roll a two and you are to be in chastity for a week.

Roll a five and I will bind you and edge you for 45 minutes.

Or maybe when you roll an odd number, you must roll again, and now there is a consequence or reward for each roll. (You rolled a five, so roll again. Next is a two, so I will bind and edge you for 45 minutes, and then put you in chastity for a week! Fun!)

The reason this appeals to me? I find the element of chance to be exciting on occasion. Though most times, your reward or punishment is of my own choosing.

~ Miss Amanda