Explain all the benefits of tidying up and how it makes you feel when you've accomplished it. And if you all do it together it's done in no time
Make them realize how much better it would be if they did, make them just consider doing it, enough to try once or twice. After a while remind them about these things and it will slowly become a habit.
Teach them to clean up what they use instantly and complete the task. Discourage half done tasks. E.g. Washing the dish after eating. Keeping the toilet tidy for the next person.
Tim Teo C.
You keep cleaning and let them get used to it. Let them watch you washing the dishes, do laundry, putting all these away. And they will get used to it. That from now on we will keep the dishes washed and the laundry basket empty. We put away things always. After 2-3 weeks they will do it themselves. Or they won't find it strange that in an odd night you ask them to wash the dishes. Nor there will be that many for them to be washed simply because you wash the dishes every day. Same for laundry. Let them see that this new cleaning crazy is not a spur of the moment, but here to stay. For them the dishes not being washed – or anything you find doing regularly now – was the norm. This is what they have seen always. Give them sometime to acclimatise. And they will follow.
I live by myself so this is tough to answer. I’d say it needs to become a habit for them, and they need to enjoy what living in a tidy space brings them . I like the mantra, outer order, inner calm. Also, I like to reward myself for cleaning and tidying. I also like doing it with someone as motivation. Maybe just making them responsible for a specific task or area would help. Also, having fewer things, minimalism, makes it easier to keep a space tidy,
Have an honest conversation with them. Let them know that a clean space is important to you, that it helps reduce overall stress (and by reducing your stress, it prevents bad moods from spilling over into their lives).