I use a combination of Booking.com, Airbnb and direct booking. Using those booking sites means you only read reviews of people who have actually stayed there, but can then e-mail or phone the place directly to enquire their rates. If going to foreign parts, using a booking site may be more secure and some of the small hotels/guesthouses may not have their own websites.
Trip Advisor can be useful for reviews, but you need to look at the profile of reviewer. A number of "glowing" reviews are from posters with just one review and also one helpful vote, which is suspicious. After a bad experience with a tour company in another country, I started analysing their Trip Advisor reviews. I noticed that there were others with poor experiences, but immediately following a bad review, there would be 3 or 4 good ones, each from posters with 1 review and 1 helpful vote - very suspicious! Of course the good reviews push up the average ratings.
Obviously everyone has to post a review for the first time, but reviews from someone who has travelled a good bit, may be more reliable. Reading a negative review need not necessarily put you off - I've read one from an American complaining about lack of room service and small room in a 2 star hotel in a popular European destination. It depends what you're expecting.