No matter how familiar you are with your hosts, staying over makes you — by definition — a guest in someone else's home. An extra person in someone else's space. A gracious host will tell you to "make yourself at home," but no matter how you choose to live at your own place, there are certain things you must do to be a good houseguest in somebody else's.
Specifically good guests always, always clean up after themselves. This is not only how you get invited back, but how you take care of the hosts who are taking such good care of you.
Here are the things you should — without exception — clean in someone else's home, some of them pertaining to each day of your stay, and some of them coming into play as you prepare to leave:
Whether it's in the sink, the shower, or on the bathroom floor, always swipe up your own hair.
Even if it's just a mug or cereal bowl, never leave dishes in the sink for someone else to do. After meals, pitch in with clearing the table, loading the dishwasher, etc. Or offer to do it all yourself.
3. Personal clutter
Try to keep things like your luggage, purses, cords, Kindle, etc. in your designated space so you aren't creating extra clutter in your host's living space.
When you leave, take your own bathroom garbage out to the outside trash can.
After you've spent your last night at your host's place, strip your bed of linens and take your sheets, pillowcases, and towels to the laundry room. Offer to start the load.
6. Your bed
If you've used a fold-out sofa or an air mattress, fold it back in or let the air out of it.