For products I'll immediately start with Project Farm on YouTube and see if he's covered the thing I'm interested in. If he hasn't I'll try /r/buyitforlife. I'll look on multiple sites of retailers I've heard of for reviews of products from a manufacturer I've heard of (no "WEEJIANGBEST" on Amazon) and give conditional trust to ratings averaged from 3000 or more individual reviews. If I'm feeling wildly thorough I might visit Fakespot to vet those reviews. If the product is expensive, I might pay for a month of access to Consumer Reports. If it's really expensive, I will pay for Consumer Reports.

For services, those are local to me, so I tend to rely on fuzzy word-of-mouth stuff. I might look in the subreddit for my city, but tend more toward simply knowing the reputation of what's around me.