A guestbook is great for leaving the stress out, but I found that if I simply ask the guest upon check-out "how was it?". Usually, he will take everything out from his system and I can either thank him or explaining to him what went wrong and why.
Moreover, a good review requires cultivation all the way. What I mean is that you have to be direct and honest with the gust before he or she makes the reservation, because you Must match expectations.
Secondly, when the guest arrives you need to explain them again about your place and what it offers because you Must match expectations.
Thirdly, every day if possible ask them how was there night, and if everything is OK so you can deal with issues right there and not wait with it until they leave.
And lastly, as I said before, ask them how was it upon check-out.
Hope that helps.