Without a doubt the most influential of all discoveries is a direct introduction by a trusted third party.
When a friend endorses (or even rejects) some music, and it sets a tone for the moment and creates a memory with you, that music will always have some form of personal value to you.
This rule ultimately stays true for what accounts for “taste” Some is unarguably “genetic” and takes any detailed discussion into a complex biochemical world (beyond scope here!), and yet the vast majority of the influences on an individual's taste are unarguably “environmental.”
Be the “friend” a close personal friend, or the DJ with whom you empathize, or the director of a motion picture series you adore talking about his favorite films, if you trust that friend when they “endorse” that media, your taste will become receptive to discovery of that media. It may be that you dislike the content yourself, or you share your friend's endorsement, and that itself will have an effect on your future “trust” of this friend's endorsements.
If you want to explore the concept more fully, Rachael Botsman and Roo Rogers's book What’s Mine Is Yours talks about “trust currency” at the heart of their “collaborative consumerism” idea. It is certainly an interesting, if idealistic, way to forecast the future of economics, but some of the concepts are definitely well-evolved explorations of “trust” in social networks, and their increasing value in modern consumerism.
Once you have been “turned on” to the content directly, you are a customer at almost no “cost of acquisition” to the publisher of the content. This makes you the most valuable type of customer.