Personally I find booking .com and related sites to be so aggressive and downright manipulative (“40 people are viewing this right now!” “Your dates are super popular, 70% of hotels in this city are sold out!” Showing 5 hotels that are sold out first in order to make you feel desperate to find and book anything!) that I hate using it even though they often have the best prices. So I will do my hotel searches elsewhere and the only go to booking .com once I’ve already made a decision, to check it they have a lower price. See also agoda, trip .com, etc
At some point I gave up. It just stopped being worth it for me to save $10 here or $20 there for how much of a navigation PITA these sites are. I just stick to Kayak for booking most things now. It's simple, clean, and straight-forward and they do their best to de-bullshittify the manipulative fees that some airline portals use to artificially make the fare seem low.
Maybe I'm kidding myself but I just tune that all out. In the end I read some reviews, look at what we have (and pictures), and check the price. I've generally had good results which is why I still use them.
Buy a guidebook on Amazon. It’s worth it before a significant trip and saves time compared to sifting through dreck on the Web.
But if you’re in town for business and you happen to have a few extra minutes and you think “hey, what is there to see around here,” TripAdvisor works well enough.