You have two kinds of trends – Classic trends and Prospective trends:

Observing everyday people in the street, talking with the younger generations, and surfing Youtube are perfect for identifying classic trends.

But if you’re looking for prospective trends, Youtube isn’t the right process because once you go to Youtube it’s already too late; you have to look elsewhere.

Most of the time prospective trends are in technology and, I know it sounds kind of crazy, but I think prospective can also be found in science fiction books.