One of the biggest uncertainties with any sort of travel is if the booked accommodation will be available on arrival. Another uncertainty is whether the condition of the premises, and the location, will be as expected, and possibly even a very pleasant surprise.
My own way of judging a hotel, or any other place to sleep, may be quite different from the way you may judge a place to stay. Cleanliness, quietness, safety, trustworthiness, convenience, helpfulness, responsiveness, value for money, a very comfortable bed, calmness and freshness are important, of course. They are the absolute minimum.
Too many choices?
Having travelled extensively myself, all over the world, to many sorts of locations, there have been a few minor inconveniences from time to time, some of which seemed quite major problems during them. But, fortunately, I am yet to experience an unavailable room or a payment gone astray. Perhaps it is because I usually confirm a booking by fax and then request confirmation of its arrival by email. It was rather more difficult to do those sorts of things only a few years ago, or even impossible.
A secure way to make a payment, or even just a safe way to send credit card details, is the most essential factor of any trip. I would never book any accommodation where the owner, or a booking agency, suggests sending my credit card details by email. It shows a lack of professionalism on their part, and especially a lack of awareness of Internet security.
Who do you trust?
I think it is a good idea is to double check straight away that the payment or information has been received and the booking reconfirmed. Even then, it may be best to telephone a day or two before arriving, or even a week or two beforehand if you have booked months in advance, just to make sure you are expected.
How do you choose where to stay? Have you ever tried the tripadvisor website? How do you know whether the opinions of other people will match your own expectations and options? And how do you keep your travel arrangements, payments and financial details private, safe and secure?