@Beach-Laws0 One thing I've found is that some guests think it's okay to leave a mess and some just naturally clean up after themselves. As Andrew said, it's important to make your "please do before check-out" expectations clear, but even so, some people don't even seem to realize what consitutes clean and tidy and other people would never leave a place in a bad state even if there weren't any instructions provided. In my experience it tends to balance out. I've had guests who cleaned up so well that aside from the used towels hanging up neatly and the used bedding, you wouldn't think anyone had been in there since I cleaned. And others who couldn't seem to manage to gather up the bits of garbage all over and put them in the bin, or rinse out their empty beer bottles so they didn't attract a trail of ants.
It's kind of part and parcel of hosting, but if it's over the top dirty requiring hours more cleaning or they've ruined things, then you could charge for extra cleaning time or damages if you feel it's worth it. Otherwise just call out their disrespect in the review and ratings.
Don't be shy about writing honest reviews to warn other hosts of bad guests so they don't just get passed around from host to host, leaving disaster zones wherever they go. And be aware that hosts who don't use Instant Book can't access a guest's star ratings, so it's important to be honest in the written review as well. If you give them 2*s for cleanliness, but the review you write just says "Nice guests", because you can't bear to tell it like it is, they'll be on to trashing someone else's place next.
But do be careful how you word things- if you outright accuse a guest of theft, the review could be removed- if you say "There were several items missing after these guests checked out", you're just stating fact.