I have been a Superhost for a few years running at 96% 5 stars, but still pull a couple of 4 stars every year. I have tried to figure out some commonality to these and here is what I have come up with:
1. As pointed out several times during this chain, some guests rate apples and oranges: only the Four Seasons gets five stars, but never an Airbnb. Mostly older guests who grew up in a hotel mentality.
2. Some guests are just crabby or unhappy about something unrelated and you become the victim. So you get private comments like " the closet was too small" ( never heard that one before), or " the instruction manual was too long after a long drive" ( huh?), or " the garbage disposal doesn't work" ( it did before you checked in and if you had texted or called, I could have wrenched it in about one minute), or " it rained for three days and the little ants came" ( could have dealt with that too if you told me). Perhaps strangely enough, these also come from older guests.
Ironically, when there have been relatively serious system failures ( ie. the power goes out; the internet goes down; the hvac minisplit fails), virtually no guest victim has dinged me for it. I've often wondered why, but after four years of doing this, I have come up with a system that works most of the time:
1. First, you need to figure out what kind of people are going to be your "guests" and why they are here. Do they seem friendly and open in the reservation process? Do they express some kind of gratitude or excitement about coming? Or are they perfunctory, communicate little or nothing about themselves and give you the feeling that you are just the "front desk." If the latter, trouble is on the horizon and you have to deliver some kind of "extras" even if they don't take you up on them - you need to figure out what and abase yourself accordingly.
2. Make your listing as accurate as possible and NEVER promise anything that you don't deliver or may be misconstrued.
3. NEVER allow guests who are unrelated kids under 22 who are not in the military.
4. ALWAYS deliver more in terms of service and amenities than you post in your listing.
5. If anything goes wrong with the stay, promptly apologize and rebate the guest more than the problem deserves - you may lose a little money, but you can probably avoid losing a star.
6. ALWAYS check in with your guests during their stay to make sure things are going smoothly ( they won't always tell you the truth, but there's nothing you can do about that).
Ultimately, if you bust your butt to provide a quality experience, the best you can do is try to avoid the "bad" guest to start with and that is not always possible so you need to see them coming and plan accordingly. Other examples: " I know that your listing says maximum of two people, but can we bring our three year old, she can stay in the bed with us"? " Gee, I'm sorry, but my homeowner's insurance won't allow more than two people and you know how those insurance companies are. " or how about " I know that check-in is at 3 pm. but my plane lands at 7 am so can I check in early?" "Gee, I will try to accomodate you, but the cleaning is usually not finished until after 1 pm. at the earliest - you can always store your stuff in the garage. " Same with the "late" check-outs. You can see them coming. You just need to figure out the best way to deal with them.
Good luck.