Mostly word of mouth from communities/people who have somewhat similar tastes. As much as I dislike algorithms controlling most of what you see on the internet, I have them to thank for a lot of music recommendations via youtube.
Books and games I usually pick up on 'recommendation' from someone since they're longer commitments (someone talking about the game). For music and movies, I also use lists from places like rateyourmusic and imdb so I can get a sense of what that person likes by looking at the stuff I recognize.
Tomorrow Never Knows