It is particularly good to do this in the middle of the night so that anywhere the human's bare foot lands will be in a wet and sticky spot. With practice, you can often manage to zap both bare feet. Always accompany guests to the bathroom. Sometimes it is fun to mimic the human, and hop into the litter box at the same time the human is using the toilet. If one of your humans is engaged in some close activity and the other is idle, stay with the busy one.
Good cats are very helpful.
Be careful to anticipate the needs of the human. When supervising cooking, sit just behind the left heel of the cook. You cannot be seen and thereby stand a better chance of being stepped on and then picked up and comforted. For book readers, get in close under the chin, between eyes and book, unless you can lie across the book itself. For computer users, stretch across the lap and begin to purr.