Every item has its place - have you used a tool, and now you're finished and leaving? Put it back in its place.
Food spoils - are you using the fridge? Keep in mind that food starts evolving (spoiling) after a few days, so either remember about your food, or send an email to the mailing list. Visibly spoiled food will be thrown out without a notice.
The trash doesn't take itself out - is the trash can full? Don't overfill it. Go touch some grass and take a walk with the trash bag to the bins outside.
Dirty table? Wipe it, it's gonna take you just a minute, and the space will be cleaner thanks to you.
Working on a project, and created some shavings or other mess? Clean it up, and toss it into the trash can. No, the floor is not a trash can.