Earlier quoted context omitted.
Uhh.. Google Maps? Kayak/Travelocity/Expedia/Orbitz/etc/etc? If I'm staying near a business client or family I ask them. If they don't know I search. Then I see what's available on the booking sites. Tripadvisor only ever came into the picture if I was visiting a resort area where I didn't know anyone.
(Disclaimer: I work in the travel industry.) What you want to do is search on these sites and then book at the actual business's sites. Even if the fares are different, it's worth it. Ever had to try to get a flight/hotel/car changed or cancelled through Expedia or a similar site? Whatever savings you get from aggregator sites aren't worth it.
booking.com works well in that regard. When a room is cancelable and you cancel via the site it works at no cost and without hassle.
That said I have very mixed feelings about the service. For starters it's a parasitic business model, which is not very transparent or honest. I.e. places that pay higher comissions are more prominently ranked. Which is not obvious to the site user.
What's outright galling is their unfairness towards hotels. "CaptainZapp, prices in Sapporo just wen down!" after booking a hotel in Sapporo a few days in advance.
In addition to the spammy nature of such mails it's an outright lie. In that example the hotel was booked during golden week (first week in May when virtually all of Japan is on holiday) and hotel prices during golden week don't go down, ever!
It's dishonest and totally unfair towards the hotel, which I just booked.